| MWMagnet Wave Products INC | Hardwick | MA | Fabricated Metal Product Manufacturing332812 | — | ◇ UNVERIFIED |
| MEMaibec Eastern INC | Stoughton | MA | Chemical Manufacturing325510 | — | ◇ UNVERIFIED |
| MSMain Street Textiles | Fall River | MA | Textile Mills313210 | — | ◇ UNVERIFIED |
| MMMajilite Mfg INC | Lowell | MA | Textile Mills313311 | — | ◇ UNVERIFIED |
| MFMarket Forge | Everett | MA | Machinery Manufacturing333310 | — | ◇ UNVERIFIED |
| MRMark Richey Woodwork | Essex | MA | Furniture and Related Product Manufacturing337125 | — | ◇ UNVERIFIED |
| MRMark Richey Woodworking & Design INC | Newburyport | MA | Plastics and Rubber Products Manufacturing326199 | — | ◇ UNVERIFIED |
| MCMarox CORP | Holyoke | MA | Fabricated Metal Product Manufacturing332710 | — | ◇ UNVERIFIED |
| MBMason Box CO | North Attleboro | MA | Paper Manufacturing322213 | — | ◇ UNVERIFIED |
| MCMassasoit Community College | Canton | MA | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| MCMass Container CORP | Marlborough | MA | Paper Manufacturing322211 | — | ◇ UNVERIFIED |
| MHMassdot Highway Division | Boston | MA | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| MCMasse Circuit CO | Methuen | MA | Fabricated Metal Product Manufacturing332813 | — | ◇ UNVERIFIED |
| MLMass Lite Div | Plainville | MA | Nonmetallic Mineral Product Manufacturing327991 | — | ◇ UNVERIFIED |
| MFMaster Finishing and Restorat | Needham | MA | Furniture and Related Product Manufacturing337212 | — | ◇ UNVERIFIED |
| MHMaster Halco INC | Canton | MA | Primary Metal Manufacturing331222 | — | ◇ UNVERIFIED |
| MCMasters Corporation | Lowell | MA | Fabricated Metal Product Manufacturing332812 | — | ◇ UNVERIFIED |
| MOMasters of Design INC | Attleboro | MA | Miscellaneous Manufacturing339910 | — | ◇ UNVERIFIED |
| MIMastex Industries Incorporated | Holyoke | MA | Textile Mills313310 | — | ◇ UNVERIFIED |
| MDMaterials Developement Corporation | Medford | MA | Fabricated Metal Product Manufacturing332811 | — | ◇ UNVERIFIED |
| MDMaterials Development Corpora | Andover | MA | Wood Product Manufacturing321999 | — | ◇ UNVERIFIED |
| MUMaterials Unlimited INC | Templeton | MA | Textile Product Mills314110 | — | ◇ UNVERIFIED |
| MTMaterion Technologies | Newburyport | MA | Nonmetallic Mineral Product Manufacturing327113 | — | ◇ UNVERIFIED |
| MTMatheson Tri-gas | Gloucester | MA | Chemical Manufacturing325120 | — | ◇ UNVERIFIED |
| MPMatrix Products INC | Attleboro | MA | Fabricated Metal Product Manufacturing332116 | — | ◇ UNVERIFIED |
| MSMayhew Steel Products INC | Shelburne | MA | Fabricated Metal Product Manufacturing332212 | — | ◇ UNVERIFIED |
| MPM.b.o. Precast, INC. | Carver | MA | Nonmetallic Mineral Product Manufacturing327332 | 20-99 | ◇ UNVERIFIED |
| MMMckinstry Metal Works INC. | Chicopee | MA | Fabricated Metal Product Manufacturing332322 | — | ◇ UNVERIFIED |
| MEMcstowe Engineering | East Bridgewater | MA | Fabricated Metal Product Manufacturing332999 | — | ◇ UNVERIFIED |
| MCMedford Cpl, INC. | Medford | MA | Food Manufacturing311812 | 20-99 | ◇ UNVERIFIED |
| MCMerckens Chocolate CO | Mansfield | MA | Food Manufacturing311320 | — | ◇ UNVERIFIED |
| MCMerrill Communications LLC | Everett | MA | Printing and Related Support Activities323110 | — | ◇ UNVERIFIED |
| MIMetalogic Industries LLC | Southbridge | MA | Fabricated Metal Product Manufacturing332710 | — | ◇ UNVERIFIED |
| MDMicro - Dynamics | Woburn | MA | Computer and Electronic Product Manufacturing334419 | — | ◇ UNVERIFIED |
| MMMicro Mech, INC | Ipswich | MA | Electrical Equipment, Appliance & Component Manufacturing335991 | — | ◇ UNVERIFIED |
| MMMicron Medical Products | Fitchburg, City of | MA | Plastics and Rubber Products Manufacturing326113 | — | ◇ UNVERIFIED |
| MUMicro Uspd Incorporated Semiconductor Products Division | Watertown | MA | Computer and Electronic Product Manufacturing334413 | — | ◇ UNVERIFIED |
| MDMicrowave Development | Needham | MA | Computer and Electronic Product Manufacturing334419 | — | ◇ UNVERIFIED |
| MRMiddlesex Research Manufacturing Co, INC | Hudson | MA | Textile Mills313320 | — | ◇ UNVERIFIED |
| MTMide Technology Corporation | Woburn | MA | Computer and Electronic Product Manufacturing334419 | — | ◇ UNVERIFIED |
| MMMilford Mfg Services LLC | Milford | MA | Computer and Electronic Product Manufacturing334412 | — | ◇ UNVERIFIED |
| MPMillennium Pharmaceuticals INC | Cambridge | MA | Chemical Manufacturing325412 | — | ◇ UNVERIFIED |
| MCMilton Cat | Milford, Town of | MA | Machinery Manufacturing333618 | — | ◇ UNVERIFIED |
 Mini Systems Incorporated | Plainville | MA | Miscellaneous Manufacturing339999 | — | ◇ UNVERIFIED |
| MCMitre Corporation | Bedford | MA | Printing and Related Support Activities323110 | — | ◇ UNVERIFIED |
| MIMks Instruments | Wilmington | MA | Computer and Electronic Product Manufacturing334519 | — | ◇ UNVERIFIED |
| MIMks Instruments INC | Andover | MA | Machinery Manufacturing333242 | — | ◇ UNVERIFIED |
| MAModern Aluminum Anod | N Adams | MA | Fabricated Metal Product Manufacturing332813 | — | ◇ UNVERIFIED |
| MAModern Aluminum Anodizing | North Adams | MA | Fabricated Metal Product Manufacturing332812 | — | ◇ UNVERIFIED |
| MTModerna Therapeutics | Cambridge | MA | Chemical Manufacturing325413 | — | ◇ UNVERIFIED |
