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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K ( Mark One ) [ X ] ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 . [ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from DELAWARE ( State or other jurisdiction of incorporation or organization ) 997 LENOX DRIVE , SUITE 100 , LAWRENCEVILLE , NJ ( Address of Principal Executive Offices ) or Title of each class Common Stock , Par Value $ 0.01 Per Share CELSION CORPORATION ( Exact Name of Registrant as Specified in Its Charter ) to Commission file number : 001-15911 Large Accelerated Filer Non - accelerated Filer [ ] [ ] 52-1256615 ( I.R.S. Employer Identification No. ) Registrant's telephone number , including area code : ( 609 ) 896-9100 Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) CLSN 08648 ( Zip Code ) Name of each exchange on which registered NASDAQ CAPITAL MARKET 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 Section 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 , 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 . Accelerated Filer Smaller Reporting Company [ X ]