As filed with the Securities and Exchange Commission on November 27, 2018

Registration No. 333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

SYNEOS HEALTH, INC.

(Exact name of registrant as specified in its charter)

1030 Sync Street

Morrisville, North Carolina 27560

Telephone: (919) 876-9300

Facsimile: (919) 876-9360

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Alistair Macdonald, Chief Executive Officer

1030 Sync Street

Morrisville, North Carolina 27560

Telephone: (919) 876-9300

Facsimile: (919) 876-9360

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Donald R. Reynolds, Esq.

Andrew J. Gibbons, Esq.

Wyrick Robbins Yates & Ponton LLP

4101 Lake Boone Trail, Suite 300

Raleigh, North Carolina 27607

Telephone: (919) 781-4000

Facsimile: (919) 781-4865

From time to time after the effective date of this Registration Statement.

(Approximate date of commencement of proposed sale to the public)

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box.  ☐

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box.  ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.  ☒

If this Form is a post-effective amendment filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of Securities Act.  ☐

CALCULATION OF REGISTRATION FEE

PROSPECTUS

SYNEOS HEALTH, INC.

Class A Common Stock

We may offer and sell shares of our Class A common stock, or common stock, from time to time in amounts, at prices and on terms that will be determined at the time of the offering. The selling stockholders to be named in a prospectus supplement may also offer and sell shares of our common stock from time to time in one or more offerings in amounts, at prices and on terms that will be determined at the time of such offerings. We will not receive any of the proceeds from the sale of our common stock by selling stockholders.

This prospectus describes the general manner in which these shares of our common stock may be offered and sold. More specific information, including the manner in which shares of common stock may be offered and sold and the prices and the net proceeds from the sales of such common stock will be described in a prospectus supplement to this prospectus. In the case of an offering by selling stockholders, information about the selling stockholders, including the relationship between the selling stockholders and us, will also be included in the applicable prospectus supplement. The prospectus supplement or free writing prospectus may also add, update or change information contained in this prospectus.

You should carefully read this prospectus and any accompanying prospectus supplement, together with documents we incorporate by reference, before you invest in our common stock. This prospectus may not be used to sell shares of our common stock unless accompanied by a prospectus supplement.

Investing in our common stock involves risks. See “Risk Factors” beginning on page 3, in any accompanying prospectus supplement and in the documents incorporated by reference into this prospectus to read about factors you should consider before investing in our common stock.

Our Class A common stock is listed on the NASDAQ Global Select Market, or NASDAQ, under the symbol “SYNH.”

Neither the Securities and Exchange Commission nor any other regulatory body has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this Prospectus is November 27, 2018.

TABLE OF CONTENTS

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement on Form S-3 that we filed with the United States Securities and Exchange Commission, or the SEC, as a “well-known seasoned issuer” as defined under Rule 405 under the Securities Act of 1933, as amended, or the Securities Act, using a “shelf” registration process. By using a shelf registration statement, we and/or the selling stockholders to be named in a prospectus supplement to this prospectus may, as applicable, from time to time, sell shares of our common stock in one or more offerings. Each time that we and/or the selling stockholders sell securities under this shelf registration statement, we will provide a prospectus supplement that will contain specific information about the terms of that offering. A prospectus supplement may also add, update or change information contained in this prospectus with respect to that offering, including information about the selling stockholders. If there is any inconsistency between the information in this prospectus and an applicable prospectus supplement, you should rely on the prospectus supplement. Before purchasing any securities, you should carefully read both this prospectus and any applicable prospectus supplement or free writing prospectus we file with the SEC, together with the additional information described under the headings “Where You Can Find More Information” and “Incorporation of Documents by Reference.”

The rules of the SEC allow us to incorporate by reference information into this prospectus. This means that important information is contained in other documents that are considered to be a part of this prospectus. Additionally, information that we file later with the SEC will automatically update and supersede this information. You should carefully read both this prospectus and the applicable prospectus supplement together with the additional information that is incorporated or deemed incorporated by reference in this prospectus. See “Incorporation of Documents by Reference” before making an investment in our common stock. This prospectus contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of the documents referred to herein have been filed or will be filed or incorporated by reference as exhibits to the registration statement of which this prospectus is a part. The registration statement, including the exhibits and documents incorporated or deemed incorporated by reference in this prospectus, can be read on the SEC website or at the SEC offices mentioned under the heading “Where You Can Find More Information.”

THIS PROSPECTUS MAY NOT BE USED TO SELL ANY SHARES OF OUR COMMON STOCK UNLESS ACCOMPANIED BY A PROSPECTUS SUPPLEMENT.

Neither the delivery of this prospectus or any applicable prospectus supplement nor any sale made using this prospectus or any applicable prospectus supplement implies that there has been no change in our affairs or that the information in this prospectus or in any applicable prospectus supplement is correct as of any date after their respective dates. You should not assume that the information included in or incorporated by reference in this prospectus or any applicable prospectus supplement or any free writing prospectus prepared by us, is accurate as of any date other than the date(s) on the front covers of those documents. Our business, financial condition, results of operations and prospects may have changed since those dates.

You should rely only on the information contained in or incorporated by reference in this prospectus or a prospectus supplement. We have not authorized anyone to give you different information, and if you are given any information that is not contained or incorporated by reference in this prospectus or a prospectus supplement, you must not rely on that information. We and any selling stockholders are not making an offer to sell securities in any jurisdiction where the offer or sale of such securities is not permitted.

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We have filed or incorporated by reference exhibits to the registration statement of which this prospectus is a part. You should read the exhibits carefully for provisions that may be important to you.

Unless the context requires otherwise, references to “our company,” “we,” “us” and “our” refer to Syneos Health, Inc. and its direct and indirect subsidiaries. Unless the context otherwise requires, references to “common stock” refer to our Class A common stock. References to GAAP are to the generally accepted accounting principles of the United States. References to the “Sponsors” refer to affiliates of Advent International Corporation and affiliates of Thomas H. Lee Partners, L.P.

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RISK FACTORS

Investing in our common stock involves a high degree of risk. You should consider carefully the risks and uncertainties described in “Risk Factors” and elsewhere in our most recently filed Annual Report on Form 10-K filed with the SEC, in each case as these risk factors are amended or supplemented by subsequent Quarterly Reports on Form 10-Q that have been or will be incorporated by reference in this prospectus. The prospectus supplement relating to a particular offering of common stock may also discuss certain risks of investing in that offering. The occurrence of any of such risks may materially and adversely affect our business, financial condition, results of operations and future prospects. In such an event, the market price of our common stock could decline, and you could lose part or all of your investment.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus (including any prospectus supplement and the information incorporated or deemed to be incorporated by reference in this prospectus) and any free writing prospectus that we may provide to you in connection with an offering of our common stock described in this prospectus contains forward-looking statements within the meaning of Section 27A of the Securities Act. All statements other than statements of historical facts contained in this prospectus, including statements regarding our future results of operations and financial position, business strategy and plans and our objectives for future operations, are forward-looking statements. The words “anticipates,” “believes,” “estimates,” “expects,” “intends,” “may,” “plans,” “projects,” “should,” “targets,” “will” and the negative thereof and similar words and expressions are intended to identify forward-looking statements. Forward-looking statements are based largely on our current expectations and projections about future events and financial trends that we believe may affect our financial condition, results of operations, business strategy, short term and long term business operations and objectives, and financial needs. These forward-looking statements are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict. Moreover, we operate in a very competitive and rapidly changing environment. New risks emerge from time to time. It is not possible for our management to predict all risks, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements we may make. In light of these risks, uncertainties and assumptions, the forward-looking events and circumstances discussed in this prospectus might not occur and actual results could differ materially and adversely from those anticipated or implied in the forward-looking statements. We caution you therefore against relying on these forward-looking statements.

Some of the key factors that could cause actual results to differ from our expectations include regional, national or global political, economic, business, competitive, market and regulatory conditions and the following:

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The forward-looking statements included in this prospectus, any prospectus supplement and the documents incorporated by referenced into this prospectus are made only as of the date hereof and thereof. You should not rely upon forward-looking statements as predictions of future events. Although we believe that the expectations reflected in the forward-looking statements are reasonable, we cannot guarantee that the future results, levels of activity, performance or events and circumstances reflected in the forward-looking statements will be achieved or occur. Moreover, neither we nor any other person assumes responsibility for the accuracy and completeness of the forward-looking statements. We undertake no obligation to update publicly any forward-looking statements for any reason after the date of this prospectus or the documents incorporated by reference into this prospectus to conform these statements to actual results or to changes in our expectations, except as may be required by law.

You should read this prospectus, any prospectus supplement or the documents incorporated by reference into this prospectus with the understanding that our actual future results, levels of activity, performance and events and circumstances may be materially different from what we expect.

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THE COMPANY

We are a leading global biopharmaceutical services organization comprised of an end-to-end clinical contract research organization and contract commercial organization. We offer both standalone and integrated biopharmaceutical development and commercialization services ranging from Phase I to Phase IV clinical trial services to services associated with the commercialization of biopharmaceutical products. Our customers include small, mid-sized, and large companies in the pharmaceutical, biotechnology, and medical device industries, and our revenue is derived through a broad suite of services designed to enhance our customers’ ability to successfully develop, launch, and market their products. We consistently and predictably deliver our services in a complex environment and offer a proprietary, operational approach to the delivery of our projects through our Trusted Process^® methodology.

On August 1, 2017, we completed a merger (the “Merger”) with Double Eagle Parent, Inc. (“inVentiv”), the parent company of inVentiv Health, Inc. under the terms of the merger agreement, dated May 10, 2017.

We are a Delaware corporation and were established as INC Research in 1998. As a result of a corporate reorganization in connection with a business combination transaction, INC Research Holdings, Inc. was incorporated in Delaware in August 2010. We changed our name to Syneos Health, Inc. after the Merger. Our principal executive office is currently located at 1030 Sync Street, Morrisville, North Carolina 27560. Our telephone number at our principal executive office is (919) 876-9300. Our common stock is currently traded on the NASDAQ under the stock symbol “SYNH”. Our corporate website is www.syneoshealth.com. The information contained on our website or that can be accessed through our website neither constitutes part of this prospectus nor is incorporated by reference herein.

USE OF PROCEEDS

In the case of a sale of shares of our common stock by us, the use of proceeds will be specified in the applicable prospectus supplement. In the case of a sale of shares of our common stock by any selling stockholder, we will not receive any proceeds from the sale of our common stock.

SELLING STOCKHOLDERS

Selling stockholders are persons or entities that, directly or indirectly, have acquired or will from time to time acquire from us, common stock in various private transactions. Such selling stockholders may be parties to registration rights agreements with us, or we otherwise may have agreed or will agree to register their shares of common stock for resale. The initial purchasers of our common stock, as well as their transferees, pledgees, donees or successors, all of whom we refer to as “selling stockholders,” may from time to time offer and sell the securities pursuant to this prospectus and any applicable prospectus supplement.

In addition to covering the offering of common stock by us, this prospectus covers the offering for resale of common stock by selling stockholders. Information about selling stockholders, if any, will be set forth in a prospectus supplement, in an amendment to the registration statement of which this prospectus is a part, or in other filings we make with the SEC under the Securities Exchange Act of 1934, as amended, or the Exchange Act, which are incorporated by reference into this prospectus.

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DESCRIPTION OF CAPITAL STOCK

The following discussion is a summary of the terms of our common stock, our certificate of incorporation, as amended, our amended and restated bylaws and certain applicable provisions of Delaware law, as currently in effect. This summary does not purport to be complete and is qualified in its entirety by reference to the actual terms and provision of our certificate of incorporation, as amended, and amended and restated bylaws, copies of which have been filed previously with the SEC. For more information on how you can obtain copies of our certificate of incorporation, as amended, and amended and restated bylaws, see “Where You Can Find More Information.”

Authorized Capitalization

Our authorized capital stock consists of (i) 300 million shares of Class A common stock, par value $0.01 per share, (ii) 300 million shares of Class B common stock, par value $0.01 per share, and (iii) 30 million shares of preferred stock, par value $0.01 per share.

Common Stock

As of November 21, 2018, 103,319,940 shares of our Class A common stock were outstanding and no shares of Class B common stock outstanding. Holders of our common stock are entitled to the following rights.

Voting Rights

Each share of our Class A common stock entitles its holder to one vote per share on all matters to be voted upon by the stockholders. Each share of our Class B common stock entitles its holder to one vote per share on all matters to be voted upon by stockholders, except with respect to the election or removal of directors. Holders of Class A common stock and Class B common stock vote together as a single class. There is no cumulative voting, which means that a holder or group of holders of more than 50% of the shares of our common stock can elect all of our directors.

Dividend Rights

The holders of our common stock are entitled to receive dividends when and as declared by our Board of Directors, which we refer to as the Board, from legally available sources, subject to the prior rights of the holders of our preferred stock, if any.

Conversion Rights

The shares of Class B common stock are convertible into Class A common stock, in whole or in part, at any time and from time to time at the option of the holder, on the basis of one share of Class A common stock for each share of Class B common stock, subject to adjustment for any stock splits, combinations or similar events.

Liquidation Rights

In the event of our liquidation or dissolution, the holders of our common stock will be entitled to share ratably in the assets available for distribution after the payment of all of our debts and other liabilities, subject to the prior rights of the holders of our preferred stock, if any.

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Other Rights

Certain of our common stockholders have preemptive or other rights to subscribe for additional shares. All holders of our common stock are entitled to share equally on a share-for-share basis in any assets available for distribution to common stockholders upon our liquidation, dissolution or winding up. All outstanding shares are, and all shares offered by this prospectus will be, when sold, validly issued, fully paid and nonassessable.

Preferred Stock

As of November 21, 2018, we had no shares of preferred stock outstanding. The Board is authorized, without further stockholder approval, to issue from time to time up to an aggregate of 30 million shares of preferred stock in one or more series and to fix or alter the designations, preferences, rights and any qualifications, limitations or restrictions of the shares of each such series thereof, including the dividend rights, dividend rates, conversion rights, voting rights, terms of redemption (including sinking fund provisions), redemption price or prices, liquidation preferences and the number of shares constituting any series or designations of such series. As of the date of this prospectus, we had no plans to issue any shares of preferred stock.

Registration Rights

Certain of our existing stockholders have certain registration rights with respect to our common stock pursuant to the Stockholders’ Agreements, as described below.

Anti-takeover Provisions

Our certificate of incorporation, as amended, and amended and restated bylaws contain provisions that could delay, defer or discourage transactions involving an actual or potential change in control of us or change in our management. We expect that these provisions, which are summarized below, might discourage coercive takeover practices or inadequate takeover bids. These provisions are also designed to encourage persons seeking to acquire control of us to first negotiate with the Board, which we believe may result in an improvement of the terms of any such acquisition in favor of our stockholders. However, they also give the Board the power to discourage transactions that some stockholders may favor, including transactions in which stockholders might otherwise receive a premium for their shares, or transactions that our stockholders might otherwise deem to be in their best interests. Accordingly, these provisions could adversely affect the price of our common stock.

Classified Board

Our certificate of incorporation, as amended, provides that the Board consists of 10 directors, and that the Board will be divided into three classes, with one class being elected at each annual meeting of stockholders. Each director will serve a three-year term, with termination staggered according to class. Class I consists of three directors, Class II consists of four directors, and Class III consists of three directors. The size of the Board may thereafter be fixed from time to time solely by resolution of at least a majority of the directors then in office.

Our certificate of incorporation, as amended, provides that directors may only be removed for cause by the holders of at least a majority of the voting power of all outstanding shares of common stock then entitled to vote on the election of directors. Furthermore, any vacancy on the Board, however occurring, including a vacancy resulting from an increase in the size of the Board, may only be filled by the affirmative vote of a majority of our directors then in office, even if less than a quorum. Directors nominated by a Sponsor pursuant to either of the Stockholders’ Agreements dated as of May 10, 2017, may be removed from office with or without cause by such Stockholders without a meeting.

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The classification of the Board could make it more difficult for a third party to acquire, or discourage a third party from seeking to acquire, control of our Company.

Requirements for Advance Notification of Stockholder Meetings, Nominations and Proposals

Our amended and restated bylaws provide that special meetings of the stockholders may be called only upon the request of a majority of the Board or upon the request of the Chief Executive Officer or the chair of the Board. Our amended and restated bylaws prohibit the conduct of any business at a special meeting other than (i) as specified in the notice for such meeting, (ii) brought before the meeting by or at the direction of the Board or an authorized officer or (iii) by a stockholder who complied with the notice procedures set forth in the amended and restated bylaws. These provisions may have the effect of deferring, delaying or discouraging hostile takeovers or changes in control or management of our company.

Our amended and restated bylaws establish advance notice procedures with respect to stockholder proposals and the nomination of candidates for election as directors, other than nominations made by or at the direction of the Board or a committee of the Board. In order for any matter to be “properly brought” before a meeting, a stockholder has to comply with the advance notice requirements. Our amended and restated bylaws allow the presiding officer at a meeting of the stockholders to adopt rules and regulations for the conduct of meetings which may have the effect of precluding the conduct of certain business at a meeting if the rules and regulations are not followed. These provisions may also defer, delay or discourage a potential acquirer from conducting a solicitation of proxies to elect the acquirer’s own slate of directors or otherwise attempting to obtain control of our company.

No Stockholder Action by Written Consent

Our certificate of incorporation, as amended, provides that stockholder action may be taken only at an annual meeting or special meeting of stockholders and may not be taken by written consent instead of a meeting, unless the taking of this action by written consent has been expressly approved in advance by the Board. Failure to satisfy any of the requirements for a stockholder meeting could delay, prevent or invalidate stockholder action.

Section 203 of the Delaware General Corporation Law

We are governed by the provisions of Section 203 of the Delaware General Corporation Law. In general, Section 203 prohibits a public Delaware corporation from engaging in a “business combination” with an “interested stockholder” for a period of three years after the date of the transaction in which the person became an interested stockholder unless:

A “business combination” includes mergers, asset sales, or other transactions resulting in a financial benefit to the stockholder. In general, an “interested stockholder” is a person who, together

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with affiliates and associates, owns, or within three years did own, 15% or more of the Company’s outstanding voting stock. These provisions may have the effect of delaying, deferring, or preventing a change in our control.

Corporate Opportunities

Our certificate of incorporation, as amended, provides that neither a Sponsor nor a director nominated by a Sponsor will have any obligation to offer us an opportunity to participate in business opportunities presented to such Sponsor even if the opportunity is one that we might reasonably have pursued and that, to the extent permitted by law, no Sponsor will be liable to us or our stockholders for breach of any duty by reason of any such activities. Therefore, the Sponsor is free to compete with us in the same business or similar businesses.

Amendment to Bylaws and Certificate of Incorporation

Any amendment to our certificate of incorporation, as amended, must first be approved by a majority of the Board and (i) thereafter be approved by a majority of the outstanding shares entitled to vote on the amendment, or (ii) if related to provisions regarding the classification of the Board, the removal of directors, director vacancies, forum selection for certain lawsuits or the amendment of certain provisions of our bylaws or certificate of incorporation, thereafter be approved by at least 66 2 /3% of the outstanding shares entitled to vote on the amendment. A vote of the majority of Class B common stock, voting separately, is required to change the voting rights of Class B common stock or to change their rights disproportionately to those of Class A common stock. Our bylaws may be amended (x) by the affirmative vote of a majority of the directors then in office, subject to any limitations set forth in the bylaws, without further stockholder action or (y) by the affirmative vote of at least 50.1% of the outstanding shares entitled to vote on the amendment, without further action by the Board.

Authorized but Unissued Shares

The authorized but unissued shares of our common stock and our preferred stock will be available for future issuance without any further vote or action by our stockholders. These additional shares may be utilized for a variety of corporate purposes, including future public offerings to raise additional capital, corporate acquisitions and employee benefit plans. The existence of authorized but unissued shares of our common stock and our preferred stock could render more difficult or discourage an attempt to obtain control over us by means of a proxy contest, tender offer, merger or otherwise.

Exclusive Forum

Our certificate of incorporation, as amended, provides that, subject to certain exceptions, the Court of Chancery of the State of Delaware shall be the sole and exclusive forum for certain stockholder litigation matters. However, it is possible that a court could rule that this provision is unenforceable or inapplicable.

Listing

Our Class A common stock is listed on the NASDAQ under the symbol “SYNH.”

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Computershare Trust Company, N.A.

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PLAN OF DISTRIBUTION

We and/or the selling stockholders, if applicable, may sell shares of common stock from time to time pursuant to underwritten public offerings, negotiated transactions, block trades or a combination of these methods or through underwriters or dealers, through agents and/or directly to one or more purchasers. The securities may be distributed from time to time in one or more transactions:

Each time that we or any of the selling stockholders sell securities covered by this prospectus, we will provide a prospectus supplement or supplements that will describe the method of distribution and set forth the terms and conditions of the offering of such securities, including: (1) the name or names of any underwriters, dealers or agents and the amounts of securities underwritten or purchased by each of them; (2) the public offering price of the securities and the proceeds to us and/or the selling stockholders; (3) any options under which underwriters may purchase additional securities; (4) any underwriting discounts or commissions or agency fees and other items constituting underwriters’ or agents’ compensation; (5) terms and conditions of the offering and (6) any discounts, commissions or concessions allowed or reallowed or paid to dealers.

Offers to purchase the common stock being offered by this prospectus may be solicited directly. Agents may also be designated to solicit offers to purchase the common stock from time to time. Any agent involved in the offer or sale of our common stock, and any commissions paid to them, will be identified in a prospectus supplement. We may engage in “at the market” offerings into an existing trading market in accordance with Rule 415(a)(4) under the Securities Act.

If a dealer is utilized in the sale of the securities being offered by this prospectus, the securities will be sold to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale.

If an underwriter is utilized in the sale of the securities being offered by this prospectus, an underwriting agreement will be executed with the underwriter at the time of sale and the name of any underwriter will be provided in the prospectus supplement that the underwriter will use to make resales of the securities to the public. In connection with the sale of the securities, we, the selling stockholders, or the purchasers of securities for whom the underwriter may act as agent, may compensate the underwriter in the form of underwriting discounts or commissions. The underwriter may sell the securities to or through dealers, and those dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for which they act as agent. Unless otherwise indicated in a prospectus supplement, an agent will be acting on a best efforts basis and a dealer will purchase securities as a principal, and may then resell the securities at varying prices to be determined by the dealer.

Any compensation paid to underwriters, dealers or agents in connection with the offering of the securities, and any discounts, concessions or commissions allowed by underwriters to participating dealers, will be disclosed in the applicable prospectus supplement. Underwriters, dealers and agents participating in the distribution of the securities may be deemed to be underwriters within the meaning of the Securities Act, and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions. We and the selling stockholders may each or both enter into agreements to indemnify underwriters,

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dealers and agents against civil liabilities, including liabilities under the Securities Act, or to contribute to any payments they are required to make in respect thereof and to reimburse those persons for certain expenses.

Our common stock is listed on the NASDAQ. To facilitate the offering of securities, certain persons participating in the offering may engage in transactions that stabilize, maintain or otherwise affect the price of the securities. This may include over-allotments or short sales of the securities, which involve the sale by persons participating in the offering of more securities than were sold to them. In these circumstances, these persons would cover such over-allotments or short positions by making purchases in the open market or by exercising their over-allotment option, if any. In addition, these persons may stabilize or maintain the price of the securities by bidding for or purchasing securities in the open market or by imposing penalty bids, whereby selling concessions allowed to dealers participating in the offering may be reclaimed if securities sold by them are repurchased in connection with stabilization transactions. The effect of these transactions may be to stabilize or maintain the market price of the securities at a level above that which might otherwise prevail in the open market. These transactions may be discontinued at any time.

If indicated in the applicable prospectus supplement, underwriters or other persons acting as agents may be authorized to solicit offers by institutions or other suitable purchasers to purchase the securities at the public offering price set forth in the prospectus supplement, pursuant to delayed delivery contracts providing for payment and delivery on the date or dates stated in the prospectus supplement. These purchasers may include, among others, commercial and savings banks, insurance companies, pension funds, investment companies and educational and charitable institutions. Delayed delivery contracts will be subject to the condition that the purchase of the securities covered by the delayed delivery contracts will not at the time of delivery be prohibited under the laws of any jurisdiction in the United States to which the purchaser is subject. The underwriters and agents will not have any responsibility with respect to the validity or performance of these contracts.

If at the time of any offering made under this prospectus a member of FINRA participating in the offering has a “conflict of interest” as defined in FINRA Rule 5121 (“Rule 5121”), that offering will be conducted in accordance with the relevant provisions of Rule 5121.

The specific terms of any lock-up provisions in respect of any given offering will be described in the applicable prospectus supplement.

The underwriters, dealers and agents may engage in other transactions with us, or perform other services for us, in the ordinary course of business for which they receive compensation.

Selling stockholders may also sell securities under Rule 144 under the Securities Act, if available, or pursuant to other available exemptions from the registration requirements under the Securities Act, rather than under this prospectus. Registration of the common stock covered by this prospectus does not mean that any shares of common stock will be offered or sold.

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LEGAL MATTERS

Wyrick Robbins Yates & Ponton LLP, Raleigh, North Carolina, has passed upon the validity of the shares of Class A common stock offered under this prospectus.

EXPERTS

The consolidated financial statements for the years ended December 31, 2017 and 2016 incorporated in this prospectus by reference from the Company’s Annual Report on Form 10-K for the year ended December 31, 2017, and the effectiveness of Syneos Health, Inc. and subsidiaries’ internal control over financial reporting have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their reports, which are incorporated herein by reference. Such financial statements have been so incorporated in reliance upon the reports of such firm given upon their authority as experts in accounting and auditing.

The consolidated financial statements of Double Eagle Parent, Inc. and its subsidiaries as of December 31, 2016 (Successor) and the related consolidated statements of operations, comprehensive loss, stockholders’ equity (deficit), and cash flows for the period from November 9, 2016 through December 31, 2016 (Successor), the period from January 1, 2016 through November 8, 2016 (Predecessor), and the years ended December 31, 2015 and 2014 (Predecessor), incorporated in this prospectus by reference from the Form 8-K filed by Syneos Health, Inc. on August 1, 2017, have been audited by Deloitte & Touche LLP, independent auditors, as stated in their report, which is incorporated herein by reference. Such financial statements have been so incorporated in reliance upon the reports of such firm given upon their authority as experts in accounting and auditing.

The consolidated financial statements of Syneos Health, Inc. (formerly INC Research Holdings, Inc.) for the year ended December 31, 2015 appearing in Syneos Health, Inc.’s Annual Report (Form 10-K) for the year ended December 31, 2017, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon, included therein, and incorporated herein by reference. Such financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement on Form S-3 under the Securities Act with respect to the shares of Class A common stock offered hereby. This prospectus, which constitutes part of the registration statement, does not contain all of the information set forth in the registration statement and the exhibits and schedules thereto. For further information with respect to us and the shares of Class A common stock offered hereby, you should refer to the registration statement (including this prospectus) and to the exhibits and schedules filed therewith. Statements contained in this prospectus regarding the contents of any contract or any other document that is filed as an exhibit to the registration statement are not necessarily complete, and each such statement is qualified in all respects by reference to the full text of such contract or other document filed as an exhibit to the registration statement.

We are also required to file annual, quarterly and current reports, proxy statements and other information with the SEC, some of which are incorporated by reference into this prospectus. The SEC maintains a website at www.sec.gov that contains reports, proxy and information statements and other information regarding registrants. Our SEC filings, including our registration statement and the exhibits and schedules thereto, are available on the SEC website at www.sec.gov.

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You may obtain a copy of any of our SEC filings, at no cost, by writing or telephoning us at:

Syneos Health, Inc.

1030 Sync Street

Morrisville, North Carolina 27560

(919) 876-9300

Attn: Corporate Secretary

INCORPORATION OF DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” information we file with it into our registration statement of which this prospectus is a part, which means that we can disclose important information to you by referring you to other documents. The information incorporated by reference is considered to be part of this prospectus, and information that we file later with the SEC and incorporate by reference will automatically update and supersede this information. We incorporate by reference into this prospectus the documents listed below and all future filings made by us with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Exchange Act, except for information “furnished” under Items 2.02, 7.01 or 9.01 on Form 8-K or other information “furnished” to the SEC which is not deemed filed and not incorporated in this prospectus, until the termination of the offering of securities described in the applicable prospectus supplement.

We hereby incorporate by reference the following documents:

We will provide to each person, including any beneficial owners, to whom a prospectus is delivered, upon written or oral request of any such person, a copy of the reports and documents that have been incorporated by reference into this prospectus, at no cost. Any such request should be directed to: Syneos Health, Inc., 1030 Sync Street, Morrisville, North Carolina 27560, Attention: Corporate Secretary (919) 876-9300. These documents are also available on the Investor Relations section of our website, which is located at http://www.syneoshealth.com, or as described under “Where You Can Find Additional Information” above. The reference to our website address does not constitute incorporation by reference of the information contained on our website.

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Any statement in a document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded for the purposes of this registration statement to the extent that a statement contained herein modifies or supersedes such statement. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this registration statement.

You should rely only on the information incorporated by reference or provided in this prospectus or any accompanying prospectus supplement. We have not authorized anyone else to provide you with different information.

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PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. Other Expenses of Issuance and Distribution.

The expenses, other than underwriting commissions, expected to be incurred by us in connection with the issuance and distribution of the securities being registered under this Registration Statement are estimated to be as follows:

ITEM 15. Indemnification of Directors and Officers.

The Registrant is governed by the Delaware General Corporation Law, or the DGCL. Section 145 of the DGCL provides that a corporation may indemnify any person, including an officer or director, who was or is, or is threatened to be made, a party to any threatened, pending or completed legal action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of such corporation), by reason of the fact that such person was or is an officer, director, employee or agent of such corporation or is or was serving at the request of such corporation as a director, officer, employee or agent of another corporation or enterprise. The indemnity may include expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with such action, suit or proceeding, provided such officer, director, employee or agent acted in good faith and in a manner such person reasonably believed to be in, or not opposed to, the corporation’s best interest and, for criminal proceedings, had no reasonable cause to believe that such person’s conduct was unlawful. A Delaware corporation may indemnify any person, including an officer or director, who was or is, or is threatened to be made, a party to any threatened, pending or contemplated action or suit by or in the right of such corporation, under the same conditions, except that such indemnification is limited to expenses (including attorneys’ fees) actually and reasonably incurred by such person, and except that no indemnification is permitted without judicial approval if such person is adjudged to be liable to such corporation. Where an officer or director of a corporation is successful, on the merits or otherwise, in the defense of any action, suit or proceeding referred to above, or any claim, issue or matter therein, the corporation must indemnify that person against the expenses (including attorneys’ fees) which such officer or director actually and reasonably incurred in connection therewith.

The Registrant’s certificate of incorporation, as amended, authorizes the indemnification of its officers and directors, consistent with Section 145 of the DGCL. Reference is made to

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Section 102(b)(7) of the DGCL, which enables a corporation in its original certificate of incorporation or an amendment thereto to eliminate or limit the personal liability of a director for violations of the director’s fiduciary duty, except (i) for any breach of the director’s duty of loyalty to the corporation or its stockholders, (ii) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (iii) pursuant to Section 174 of the DGCL, which provides for liability of directors for unlawful payments of dividends of unlawful stock purchase or redemptions, or (iv) for any transaction from which a director derived an improper personal benefit. As permitted by the DGCL, our certificate of incorporation, as amended, includes a provision to eliminate the personal liability of our directors for monetary damages for breach of their fiduciary duties as directors, subject to certain exceptions. In addition, our certificate of incorporation, as amended, and amended and restated bylaws provide that we are required to indemnify our officers and directors under certain circumstances, including those circumstances in which indemnification would otherwise be discretionary, and we are required to advance expenses to our officers and directors as incurred in connection with proceedings against them for which they may be indemnified.

The Registrant has entered into indemnification agreements with each of its directors and executive officers. These agreements, among other things, require the Registrant to indemnify each director and executive officer to the fullest extent permitted by Delaware law, including indemnification of expenses such as attorneys’ fees, judgments, fines and settlement amounts actually and reasonably incurred by the director or executive officer in any action or proceeding, including any action or proceeding by or in right of the Registrant, arising out of the person’s services as a director or executive officer.

The Registrant maintains directors’ and officers’ liability insurance for the benefit of its directors and officers.

ITEM 16. Exhibits.

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ITEM 17. Undertakings.

The undersigned registrant hereby undertakes:

provided, however, that paragraphs (1)(i), (1)(ii) and (1)(iii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed

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with or furnished to the Commission by the registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in this registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

The undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

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The undersigned Registrant hereby undertakes that, for purposes of determining any liability under the Securities Act of 1933, each filing of the Registrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Act and will be governed by the final adjudication of such issue.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Raleigh, State of North Carolina, on November 27, 2018.

NOW ALL MEN BY THESE PRESENTS that each individual whose signature appears below constitutes and appoints Alistair Macdonald and Jason Meggs, and each of them, any of whom may act without joinder of the other, his or her true and lawful attorneys-in-fact and agents with full power of substitution and resubstitution, for him or her and in his or her name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this registration statement, including a prospectus or an amended prospectus therein and registration statements filed pursuant to Rules 413 or 462 under the Securities Act of 1933, as amended, and to file the same, with all exhibits thereto, and all documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or their substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the dates indicated.