| Employer | State | City | |
| M&O Corporation | Connecticut | Bridgeport | View Profile |
| M.C. Dean | Virginia | Dulles | View Profile |
| Main Enterprises | Connecticut | Stratford | View Profile |
| Mann Refrigeration | Texas | Bridgeport | View Profile |
| Mar Cor Purification | Minnesota | Plymouth | View Profile |
| Marx Sheet Metal & Mechanical, Inc | Pennsylvania | Wilkes Barre | View Profile |
| Matrix Technology | Colorado | Colorado Springs | View Profile |
| McFarlane Inc. | North Dakota | Grand Forks | View Profile |
| McKenney's, Inc. | Georgia | Atlanta | View Profile |
| McKinstry Co. | Washington | Seattle | View Profile |
| McKinstry Co. | Washington | Seattle | View Profile |
| McQuay International/McQuay Service | Virginia | Staunton | View Profile |
| Mechanical Solutions, Inc. | Texas | Dallas | View Profile |
| MEP Jobs - Customer Fulfillment | Iowa | Des Moines | View Profile |
| MEP Jobs - Tom | Iowa | Des Moines | View Profile |
| Merit Services | Texas | Carrollton | View Profile |
| Merit Services | Texas | Carrollton | View Profile |
| Merrimack Valley Corporation | Massachusetts | Methuen | View Profile |
| Midway Services | Florida | Clearwater | View Profile |
| Midway Services | Florida | Clearwater | View Profile |
| Midwest Mechanical Services & Solutions | Missouri | St. Louis | View Profile |
| Millian-Aire Enterprises | Florida | New Port Richey | View Profile |
| Minuteman Plumbing & Drain Services, Inc. | California | Santa Anna | View Profile |
| Modern Controls Inc | Delaware | New Castle | View Profile |
| Monsen Engineering Company | New Jersey | Fairfield | View Profile |
| Montage Laguna Beach | California | Laguna Beach | View Profile |
| Moore Heating and Air Conditioning, Inc. | Alaska | Anchorage | View Profile |
| Moore's Electrical & Mechanical Construction, Inc. | Virginia | Alta Vista | View Profile |
| Mtech- Comfort Systems USA | Texas | Austin | View Profile |
| Murray Mechanical Services | California | Buena Park | View Profile |