As filed with the Securities and Exchange Commission on January 30, 2014

Registration No. 333-191323

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Amendment No. 8

to

Form S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

BIOCEPT, INC.

(Exact name of registrant as specified in its charter)

5810 Nancy Ridge Drive

San Diego, CA 92121

(858) 320-8200

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

Michael W. Nall

Chief Executive Officer and President

Biocept, Inc.

5810 Nancy Ridge Drive

San Diego, CA 92121

(858) 320-8200

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

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after this Registration Statement becomes effective.

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, 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 post-effective amendment filed pursuant to Rule 462(d) 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.  ¨

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

The registrant is an “emerging growth company,” as defined in Section 2(a)(19) of the Securities Act. This registration statement complies with the requirements that apply to an issuer that is an emerging growth company.

CALCULATION OF REGISTRATION FEE

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

EXPLANATORY NOTE

Biocept, Inc. has prepared this Amendment No. 8 to the Registration Statement (the “Registration Statement”) on Form S-1 (File No. 333-191323) solely for the purpose of filing Exhibits 10.13 and 10.22 to the Registration Statement. This Amendment No. 8 does not modify any provision of the prospectus that forms a part of the Registration Statement and accordingly such prospectus has not been included herein.

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

The following table sets forth the costs and expenses, other than underwriting discounts and commissions, payable in connection with the sale and distribution of the securities being registered. All amounts are estimated except the SEC registration fee, the FINRA filing fee and the NASDAQ listing fee.

Section 145 of the Delaware General Corporation Law authorizes a court to award, or a corporation’s board of directors to grant, indemnity to directors and officers in terms sufficiently broad to permit such indemnification under certain circumstances for liabilities, including reimbursement for expenses incurred, arising under the Securities Act.

The Company’s amended certificate of incorporation provides for indemnification of its directors and executive officers to the maximum extent permitted by the Delaware General Corporation Law, and the Company’s amended and restated bylaws provide for indemnification of its directors and executive officers to the maximum extent permitted by the Delaware General Corporation Law.

In addition, the Company has entered into indemnification agreements with each of its current directors and executive officers. These agreements will require the Company to indemnify these individuals to the fullest extent permitted under Delaware law against liabilities that may arise by reason of their service to the Company and to advance expenses incurred as a result of any proceeding against them as to which they could be indemnified. The Company also intends to enter into indemnification agreements with its future directors and executive officers.

In any underwriting agreement the Company enters into in connection with the sale of common stock being registered hereby, the underwriters will agree to indemnify, under certain conditions, us, the Company’s directors, the Company’s officers and persons who control us, within the meaning of the Securities Act, against certain liabilities.

Since July 1, 2010, the Registrant made sales of the unregistered securities discussed below. All common stock share, option, warrant and RSU amounts (and the exercise price of all common stock options and warrants) reflect (i) the 1-for-3 reverse common stock split effected on November 3, 2011, and (ii) the 1-for-14 reverse common stock split effected on November 1, 2013. The offers, sales and issuances of the securities described below were exempt from registration under the Securities Act by virtue of Section 4(a)(2) of the Securities Act and/or, in the case of compensatory issuances, Securities Act Rule 701, and/or, in the case of conversions, Section 3(a)(9) of the Securities Act. No commissions were paid.

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Preferred Stock Financing

From August 2010 to September 2010, the Company sold 8,939,990 shares of its Series BB preferred stock (convertible, post-recapitalization and post-reverse-splits, into 213,571 shares of the Company’s common stock), to 15 accredited investors, for aggregate gross proceeds of $5.364 million.

Note/ Warrant Financings

In 30 closings from February 2011 to November 2012, the Company sold secured convertible promissory notes with an aggregate principal amount of $12,336,247, together with warrants to purchase 4,569,030 shares of its preferred stock (convertible, post-reverse-splits, into 108,786 shares of the Company’s common stock), to 11 accredited investors, for aggregate gross proceeds of $12,336,247.

In 21 closings from January 2012 to December 2012, the Company sold promissory notes with an aggregate principal amount of $5,960,000, together with warrants to purchase 2,207,401 shares of its preferred stock (convertible, post-reverse-splits, into 52,557 shares of the Company’s common stock) to five accredited investors, for aggregate gross proceeds of $5,960,000.

In 52 closings from December 2012 to December 31, 2013, the Company sold promissory notes with an aggregate principal amount of $4,990,000, together with warrants to purchase an indeterminate number of shares of the Company’s common stock, to 12 accredited investors, for aggregate gross proceeds of $4,990,000.

Compensatory Issuances

In the last six months of 2010 the Company issued 50,600 common stock options (at a $4.62 exercise price per share) and 390,000 preferred stock restricted stock units to service providers.

In 2011 the Company issued 36,260 common stock options (at a $4.62 exercise price per share), 12,753 common stock restricted stock units and 1,002,705 preferred stock restricted stock units to service providers.

In 2012 the Company issued 332 common stock options (at a $4.62 exercise price per share) and 41,857 common stock restricted stock units to service providers.

In 2013, the Company issued 300,438 common stock options (at a $5.18 exercise price per share) and 101,559 common stock restricted stock units to approximately 35 service providers.

Inducement Warrants

In September 2012, the Company issued 66,666 Series A preferred stock warrants, at an exercise price of $0.60 per share, to its landlord in exchange for certain real estate lease accommodations.

In June 2013, the Company issued 23,810 common stock warrants, at an exercise price to be determined in accordance with contract, to a lender (a 5% beneficial shareholder) in connection with a note conversion.

In July through October 2013, the Company issued an indeterminate number of common stock warrants, at an exercise price to be determined in accordance with contract, to three guarantors in connection with their guaranties of its UBS Bank USA revolving line of credit.

In September 2013, the Company issued an indeterminate number of common stock warrants, at an exercise price to be determined in accordance with contract, to its landlord in connection with a lease amendment.

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Recapitalization

In November 2011, the Company effected a recapitalization in which all outstanding shares of, and warrants to purchase and restricted stock units to obtain, the Company’s outstanding Series AA preferred stock and Series BB preferred stock were converted into the same number of shares of, warrants to purchase and restricted stock units to obtain, Series A preferred stock. At the same time, the Company effected the 1-for-3 reverse split of its common stock.

Conversions and Exercises

In November 2011, the Company’s Executive Chairman exercised 10,204 common stock options, paying an aggregate exercise price of $47,183.

In October 2011, a major shareholder converted 2,064,520 shares of Series AA preferred stock into 49,155 shares of common stock.

In March and April 2013, two employees exercised 85 common stock options, paying an aggregate exercise price of $395.

In June 2013, the holders of promissory notes with an aggregate principal balance of approximately $20,231,000 and accrued but unpaid interest of approximately $2,591,000 voluntarily converted such principal and interest into 42,245,834 shares of the Company’s Series A preferred stock.

In the fourth quarter of 2013, four employees exercised 3,936 common stock options, paying an aggregate exercise price of $19,710.

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EXHIBITS

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All exhibits not marked with a single, double, triple, quadruple or quintuple pound sign (#) were filed with the issuer’s September 23, 2013 Registration Statement on Form S-1.

No financial statement schedules are provided because the information is not required or is shown either in the financial statements or the notes thereto.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to our directors, officers and controlling persons pursuant to the foregoing provisions, or otherwise, we have been advised that in the opinion of the SEC 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 us of expenses incurred or paid by one of our directors, officers or controlling persons 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, we will, unless in the opinion of counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by us is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

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The undersigned Registrant hereby undertakes to provide to the underwriters, at the closing specified in the underwriting agreement, certificates in such denominations and registered in such names as required by the underwriters to permit prompt delivery to each purchaser.

The undersigned Registrant hereby undertakes that:

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SIGNATURES

Pursuant to the requirements of the Securities Act, the Registrant has duly caused this Amendment No. 8 to Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in San Diego, California, on the 30th day of January, 2014.

Pursuant to the requirements of the Securities Act, this Amendment No. 8 to Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

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EXHIBIT INDEX

All exhibits not marked with a single, double, triple, quadruple or quintuple pound sign (#) were filed with the issuer’s September 23, 2013 Registration Statement on Form S-1.