UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 13F FORM 13F COVER PAGE Report for the Calendar Year or Quarter Ended: March 31, 2013 Check here if Amendment[ ] Amendment Number: This Amendment Check only one:[ ]is a restatement [ ]adds new holdings entries. Institutional Investment Manager Filing this Report: Name: ACK Asset Management LLC Address: 2 Overhill Road, Suite 400, Scarsdale, NY 10583 Form 13F File Number: 28-14060 The institutional investment manager filing this report and the person by whom it is signed hereby represent that the person signing the report is authorized to submit it, that all information contained herein is true, correct and complete,and that it is understood that all required items, statements, schedules, lists, and tables, are considered integral parts of this form. Person Signing this Report on Behalf of Reporting Manager: Name: Kenneth F. Cooper Title: Chief Financial Officer Phone: 914 220-8340 Signature Place Date of Signing: Kenneth F. Cooper Scarsdale, NY May 13, 2013 Report Type [X] 13F HOLDINGS REPORT. (Check here if all holdings of this reporting manager are reported in this report.) [ ]13F NOTICE. (Check here if no holdings reported are in this report, and all holdings are reported by other reporting manager(s).) [ ]13F COMBINATION REPORT. (Check here if a portion of the holdings for this reporting manager are reported in this report and a portion are reported by other reporting manager(s).) List of Other Managers Reporting for this Manager: NONE FORM 13F SUMMARY PAGE Report Summary: Number of Other Included Managers: 0 Form 13F Information Table Entry Total: 35 Form 13F Information Table Value Total: 230,563 (thousands) List of Other Included Managers: Provide a numbered list of the name(s) and Form 13F file number(s) of all institutional investment managers with respect to which this report is filed, other than the manager filing this report. NONE COL 1 COL 2 COL 3 COL 4 COL 5 COL 6 COL 7 COL 8 Vot Auth Name of Issuer Title CUSIP Value SHRS/PRN AMT SH/PRN P/CA Invest O Mgr SOLE SHARED NONE (X1,000) Discre ASCENT CAPITAL GROUP INC CL A 43632108 4,747 63,769 SH SOLE 63,769 ASTRONICS CORP COM 46433108 10,494 351,900 SH SOLE 351,900 ARMSTRONG WORLD INDUSTRIES COM 04247X102 6,707 120,000 SH SOLE 120,000 BALCHEM CORP COM 57665200 9,544 217,200 SH SOLE 217,200 BLACK DIAMOND INC COM 09202G101 7,229 793,509 SH SOLE 793,509 CLEAN HARBORS INC COM 184496107 12,257 211,000 SH SOLE 211,000 CAPITAL SENIOR LIVING CORP COM 140475104 10,228 386,989 SH SOLE 386,989 EXAMWORKS GROUP INC COM 30066A105 5,861 338,417 SH SOLE 338,417 FLOW INTL CORP COM 343468104 5,465 1,397,600 SH SOLE 1,397,600 FXCM INC CL A 302693106 4,911 359,000 SH SOLE 359,000 GREENBRIER COMPANIES INC COM 393657101 5,007 220,477 SH SOLE 220,477 GRIFFON CORP COM 398433102 4,804 403,000 SH SOLE 403,000 GRAHAM CORP COM 384556106 2,195 88,725 SH SOLE 88,725 GLOBAL POWER EQUIPMENT GROU CL A 371559105 3,808 40,900 SH SOLE 40,900 KIRBY CORP COM 497266106 10,983 143,010 SH SOLE 143,010 KENNEDY-WILSON HOLDINGS INC COM 489398107 10,147 654,200 SH SOLE 654,200 GLADSTONE LAND CORP COM 376549101 3,270 210,700 SH SOLE 210,700 LIBBEY INC COM 529898108 16,469 852,000 SH SOLE 852,000 MEASUREMENT SPECIALTIES INC COM 583421102 9,390 236,100 SH SOLE 236,100 RESPONSYS INC COM 761248103 2,231 252,100 SH SOLE 252,100 MUELLER INDUSTRIES INC COM 624756102 6,901 129,500 SH SOLE 129,500 NCI BUILDING SYSTEMS INC COM 628852204 5,135 295,611 SH SOLE 295,611 ORION MARINE GROUP INC COM 68628V308 8,085 813,400 SH SOLE 813,400 POWELL INDUSTRIES INC COM 739128106 3,228 61,404 SH SOLE 61,404 PRIMORIS SERVICES CORP COM 74164F103 9,885 447,100 SH SOLE 447,100 ROGERS CORP COM 775133101 7,691 161,517 SH SOLE 161,517 ROADRUNNER TRANSPORTATION SY COM 76973Q105 3,963 172,300 SH SOLE 172,300 S&W SEED CO COM 785135104 4,939 469,890 SH SOLE 469,890 US SILICA HOLDINGS INC COM 90346E103 7,664 325,000 SH SOLE 325,000 SWIFT TRANSPORTATION CO COM 87074U101 2,482 175,000 SH SOLE 175,000 INTERFACE INC COM 458665304 6,900 359,000 SH SOLE 359,000 TRINITY BIOTECH PLC SPON ADR 896438306 10,344 612,800 SH SOLE 612,800 UMH PROPERTIES INC COM 903002103 3,940 383,600 SH SOLE 383,600 ISHARES RUSSELL 04/20/2013 COM 1,287 11,000 PUT SOLE 11,000 35 230,563