UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 10-K/A

(Amendment No. 1)

For the fiscal year ended December 31, 2019

For the transition period from            to

Commission file number 001-38709

Osmotica Pharmaceuticals plc

(Exact name of registrant as specified in its charter)

400 Crossing Boulevard

Bridgewater, NJ 08807

(Address of principal executive offices)

(Zip Code)

(908) 809-1300

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ¨ No x

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. Yes ¨ No x

Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x No ¨

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes x No ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See 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 13(a) of the Exchange Act. x

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ¨ No x

The aggregate market value of the voting shares held by non-affiliates of the Registrant on June  28, 2019, based upon the closing price of $3.80 of the Registrant’s ordinary shares as reported on the Nasdaq Global Select Market, was approximately $30.3 million.

Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest practicable date.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s definitive Proxy Statement for the 2020 Annual Meeting of Shareholders have been filed with the Securities and Exchange Commission pursuant to Regulation 14A and are incorporated by reference in Part III Items 10-14 of this Annual Report on Form 10-K.

EXPLANATORY NOTE

This Amendment No. 1 (the “Amendment”) to the Annual Report on Form 10-K of Osmotica Pharmaceuticals plc (the “Company”) for the fiscal year ended December 31, 2019, originally filed with the Securities and Exchange Commission (the “SEC”) on March 19, 2020 (the “Original Filing”), is being filed solely to include revised Exhibits 31.1 and 31.2, which include certain statements required by Item 601(b)(31) of Regulation S-K inadvertently omitted by the Company when originally filed. This Amendment contains only the cover page, this explanatory note, the exhibit index, the signature page and the revised exhibits. Because no financial statements are included with this Amendment, paragraph 3 of the certifications in Exhibits 31.1 and 31.2 has been omitted.

Except for the foregoing, this Amendment does not alter or update any information contained in the Original Filing. The Original Filing continues to speak as of the date of the Original Filing, and the Company has not updated the disclosures contained therein to reflect any events that have occurred as of a date subsequent to the date of the Original Filing. Accordingly, this Amendment should be read in conjunction with the Original Filing and the Company’s filings made with the SEC subsequent to the Original Filing

ITEM 15. EXHIBITS AND FINANCIAL STATEMENT SCHEDULES

(a) The following documents are filed as a part of this Amendment.

(3) The following exhibits:

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.