Sec Form 4 Filing - THIBAUD DIDIER M C @ MERCURY SYSTEMS INC - 2015-05-26

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person THIBAUD DIDIER M C 2. Issuer Name and Ticker or Trading Symbol MERCURY SYSTEMS INC [ MRCY] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) President, MCE (Last) (First) (Middle) 201 RIVERNECK ROAD 3. Date of Earliest Transaction (MM/DD/YY) 05/26/2015 (Street) CHELMSFORD, MA01824 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 05/26/2015 M 12,839 ( 1 ) A $ 8.62 371,954 D Common Stock 05/26/2015 S 12,839 ( 1 ) D $ 13.525 359,115 D Common Stock 05/27/2015 M 18,161 ( 1 ) A $ 8.62 377,276 D Common Stock 05/27/2015 S 18,161 ( 1 ) D $ 13.541 359,115 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Non-Qualified Stock Option (Right to buy) $ 8.62 05/26/2015 M 12,839 ( 1 ) 06/10/2012 06/10/2015 Common 12,839 $ 0 ( 2 ) 18,161 D Non-Qualified Stock Option (Right to buy) $ 8.62 05/27/2015 M 18,161 ( 1 ) 06/10/2012 06/10/2015 Common 18,161 $ 0 ( 2 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other THIBAUD DIDIER M C 201 RIVERNECK ROAD CHELMSFORD, MA01824 President, MCE Signatures Charles A. Speicher (Attorney-in-fact) 05/28/2015 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The exercise of the stock option and sale of the underlying shares reported herein was pursuant to a 10b5-1 trading plan for a stock option expiring on June 10, 2015. The Company's 2005 Stock Incentive Plan does not contain a net exercise feature for stock options and accordingly the option was exercised in full. ( 2 )Field N/A to this transaction but was completed to allow for electronic filing only.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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