| Main Street Management | Main Street Management | — | (707) 252-2022 | Property managers | Napa · Napa County | — | — |
| Major Fire Systems INC | Timothy Alan Major | — | (707) 290 1201 | Other | American Canyon · Napa County | — | — |
| Manriquez Painting | Manriquez Painting | — | (707) 259 0677 | Windows, patio, painters | Napa · Napa County | — | — |
| Manzanita Building Group INC | Thomas Alfred Trainor | — | (707) 291 6540 | GC, remodel, ADU | St Helena · Napa County | — | — |
| Marceau Fire Protection INC | Lannie Don Marceau | — | (925) 250 1854 | Other | Napa · Napa County | — | — |
| Marin Heating And Air | Marin Heating And Air | marinheatingac@gmail.com | (415) 748-0081 | HVAC | Fairfax · Napa County | — | — |
| Mario Brothers Plumbing INC | Rodriguez Amauri Grajales | — | (707) 236 4462 | Other | Calistoga · Napa County | — | — |
| Mario Custom Builder INC | Hernandez Mario | — | (707) 501 7831 | GC, remodel, ADU | Napa · Napa County | — | — |
| Mark Aman Construction INC | Mark Steven Aman | jacob.theo.aman@gmail.com | (707) 738-3890 | GC, remodel, ADU | Napa · Napa County | — | — |
| Mark Evans | Mark Evans | — | (707) 494 6534 | Other | Napa · Napa County | — | — |
| Mark Foerder Floor Coverings INC | Mark Alan Foerder | — | (707) 888 3826 | Other | Napa · Napa County | — | — |
| Mark Peterson | Mark Peterson | — | (707) 963 7828 | GC, remodel, ADU | St Helena · Napa County | — | — |
| Mark's Painting | Mark's Painting | — | (707) 337 7895 | Windows, patio, painters | Napa · Napa County | — | — |
| Martinez Painting | Martinez Painting | info@martinez-painting.com | (707) 295 4418 | Windows, patio, painters | Napa · Napa County | — | — |
| Mastercraft Tile INC | Mark William Downing | — | (707) 363 9018 | Other | Napa · Napa County | — | — |
| Matt Smith Builders | Matt Smith Builders | — | (707) 815 4036 | GC, remodel, ADU | St Helena · Napa County | — | — |
| Matthew Scott Construction | Matthew Michael Scott | — | (707) 372 4090 | GC, remodel, ADU | Napa · Napa County | — | — |
| Matthew Simas | Matthew Simas | — | (707) 478 8837 | Other | Napa · Napa County | — | — |
| Matthew Stubbs Home Improvement Construction | Matthew Thomas Stubbs | — | (707) 812 0515 | GC, remodel, ADU | Napa · Napa County | — | — |
| Mavericks Builders INC | Robin Nielsen | robin@mavericksbuilders.com | (415) 604 0070 | GC, remodel, ADU | Napa · Napa County | — | — |
| Mazariegos Construction | Wilder Natan Mazariegos | — | (415) 987 5116 | GC, remodel, ADU | American Canyon · Napa County | — | — |
| Mc Collum General Engineering | Mc Collum General Engineering | — | (707) 252 6220 | Other | Yountville · Napa County | — | — |
| Mc Construction And Concrete LLC | Michael Glenn Connor | — | (707) 265 8317 | GC, remodel, ADU | Napa · Napa County | — | — |
| Mc Cornack Associates Construction INC | Clark Wellwood Jr Mc Cornack | — | (707) 481 5080 | GC, remodel, ADU | St Helena · Napa County | — | — |
| Mc Daniel Mechanical Construction INC | Anthony Paul Mc Daniel | — | (707) 529 9005 | Other | Napa · Napa County | — | — |
| Mc Lean & Williams INC | Sherry Lynn Salinas | — | (707) 255 6450 | Other | Napa · Napa County | — | — |
| Mc Michael Building Service & Repair | Steve Jeffrey Mc Michael | — | (707) 501 7364 | Electricians | Napa · Napa County | — | — |
| Mcgrath Builders | Mcgrath Builders | — | (925) 212 7196 | GC, remodel, ADU | St Helena · Napa County | — | — |
| Mckay Builders | Michael Edward Mckay | — | (707) 287 0649 | GC, remodel, ADU | Calistoga · Napa County | — | — |
| Mcnay's Precision Woodworks INC | Michael Robert Mc Nay | — | (707) 255 4773 | Other | Napa · Napa County | — | — |
| Mel Electric INC | Matthew Brandon Lopez | — | (707) 666 2976 | Electricians | Napa · Napa County | — | — |
| Michael Cerasoli | Michael Cerasoli | — | (707) 287 0863 | GC, remodel, ADU | Napa · Napa County | — | — |
| Michael Meza | Michael Meza | — | (707) 332 6826 | Other | Napa · Napa County | — | — |
| Michael Quast | Michael Quast | — | (707) 737 5042 | GC, remodel, ADU | Calistoga · Napa County | — | — |
| Michael Walker Construction INC | Michael Don Walker | — | (707) 249 5906 | GC, remodel, ADU | Napa · Napa County | — | — |
| Michelon Construction | Steven Allen Michelon | — | (707) 484 8239 | GC, remodel, ADU | Napa · Napa County | — | — |
| Mike A Leontini | Mike A Leontini | — | (707) 294 3668 | Tree | Napa · Napa County | — | — |
| Mike Coultrup Construction | Michael Phillip Coultrup | — | (707) 815 0700 | GC, remodel, ADU | Napa · Napa County | — | — |
| Mike De Simoni | Mike De Simoni | — | (510) 719 1393 | GC, remodel, ADU | Napa · Napa County | — | — |
| Mike Lowater Tractor Works | Mike Lowater Tractor Works | — | (707) 315 6980 | Other | Pope Valley · Napa County | — | — |