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Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 Form 10 - K × ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 OR □ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from Massachusetts to Commission file number 001-33912 Enterprise Bancorp , Inc. ( Exact name of registrant as specified in its charter ) ( State or other jurisdiction of incorporation of organization ) 222 Merrimack Street , Lowell , Massachusetts ( Address of principal executive offices ) ( 978 ) 459-9000 Registrant's telephone number , including area code 04-3308902 ( IRS Employer Identification No. ) 01852 ( Zip code ) Securities registered pursuant to Section 12 ( b ) of the Exchange Act : Title of each class Common Stock , $ 0.01 par value per share Trading Symbol ( s ) EBTC Name of each exchange on which registered NASDAQ Stock Market Securities registered pursuant to Section 12 ( g ) of the Exchange Act : NONE Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . o Yes ý No Indicate by check mark if the registrant is not required to file pursuant to Section 13 or Section 15 ( d ) of the Act . o Yes ý No 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 . ý Yes o 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 ) . ý Yes o No 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 definition of " large accelerated filer , " " accelerated filer , " " smaller reporting company , " and " emerging growth company " in Rule 12b - 2 of the Exchange Act ( Check one ) : Large accelerated filer Accelerated filer x Non - accelerated filer Smaller reporting company Emerging growth company □ 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 . ☐ Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) □ Yes ý No ☑ State the aggregate market value of the voting and non - voting common equity held by non - affiliates computed by reference to the price at which the common equity was last sold , or the average bid price and asked price of such common equity , as of the last business day of the registrant's most recently completed second fiscal quarter : $ 233,944,867 ( $ 23.82 per share ) as of June 30 , 2020 , the last trading day of the registrant's most recently completed second quarter . Indicate the number of shares outstanding of each of the registrant's classes of common stock , as of the latest practicable date : March 1 , 2021 , Common Stock , par value $ 0.01 , 11,957,927 shares outstanding DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant's definitive proxy statement for its annual meeting of stockholders to be held on May 4 , 2021 are incorporated by reference in Part III of this Form 10 - K .