| JMSF Construction | B | 2026 | Active |
| Joe Badger Construction Inc | B | 2024 | Active |
| Josh Woods Construction LLC | B | 2021 | Active |
| Jrcal Construction Inc | A | 2025 | Active |
| Kabine Construction Inc | B | 2013 | Active |
| Kaelin Construction | B | 2010 | Active |
| Kaikaina Construction Inc | B | 2018 | Active |
| Kanteco Construction Group Inc | B | 2020 | Active |
| Keegan And Coppin Builders Inc | B | 1982 | Active |
| Kekas Plumbing Inc | B + C36 | 2020 | Active |
| Kelly Cowan Designs Professional Corporation | B | 2007 | Active |
| Keyspade Builders Inc | B | 2018 | Active |
| Kilcor Builders & Design Inc | B | 2003 | Active |
| Kimrick | B | 1997 | Active |
| King Construction & General Engineering Inc | A, B | 1986 | Active |
| Kings Valley Builders Inc | B | 2023 | Active |
| Kirby Construction | B | 2002 | Active |
| Kline Robert Construction Inc | B + C8 | 2003 | Active |
| Kobilt Inc | B | 2006 | Active |
| Koch Construction Company Inc | B | 1996 | Active |
| Korson Homes Inc | B | 2006 | Active |
| L B L Construction Inc | B + C36 | 2001 | Active |
| L F G | B | 2024 | Active |
| Lanway Construction Company Inc | A | 1999 | Renew by Nov 30, 2026 |
| Lerdahl J Construction | B | 2003 | Active |
| Log Prince Construction Inc | B | 2012 | Active |
| Lotus Construction Inc | B + C47 | 2007 | Active |
| Luce Excavation Inc | A | 2000 | Active |
| M B Homes Sonoma LLC | A, B + C8 | 2018 | Active |
| M G Pro Builders Inc | B | 2022 | Active |
| M G R Plumbing Inc | B + C36 | 2017 | Active |
| M M H C Inc | B + C47 | 2006 | Active |
| M's General Construction Inc | B | 2025 | Active |
| M3 Integrated Services Inc | A, B | 2011 | Active |
| Main Street Place Corp | B | 1993 | Active |
| Maky's Home Pro Construction Inc | B | 2024 | Renew by Nov 30, 2026 |
| Manor Development Co | B | 1959 | Active |
| Manzo Construction LLC | B | 2025 | Active |
| Marlboro Construction Company | B + C8 | 2021 | Active |
| Marovich Homes Inc | B + C9 | 1990 | Active |
| Martin Custom General Engineering Inc | A | 2019 | Active |
| Master Builds Construction | B | 2022 | Active |
| Masterstouch Construction Inc | B | 2007 | Active |
| MC Cannell Construction Inc | B | 1978 | Active |
| MC Clish M A Excavating Inc | A | 1991 | Active |
| MC Donald Gary & Son Inc | A | 1973 | Renew by Nov 30, 2026 |
| MC Gillicuddy Construction | B | 2006 | Active |
| MC Intosh Builders Inc | B | 1988 | Active |
| McChinak Incorporated | B | 1992 | Active |
| McClure Jason Contracting Inc | B | 2015 | Active |
| McCluskey Engineering Inc | A + HAZ | 2017 | Active |
| McMasters Construction Inc | B | 2026 | Active |
| McMinn Construction Group LLC | B | 2025 | Active |
| McPheron Construction Inc | B | 2023 | Active |
| McVay Heritage Construction LLC | B | 2026 | Active |
| Merciari Construction Design | B | 2019 | Active |
| Metal Roof Systems Inc | B + C39 | 1989 | Active |
| MH Plus Inc | B | 2018 | Active |
| Mikara Construction Inc | B | 2007 | Active |
| Mike's Home Repair And Maintenance LLC | B | 2021 | Active |
| MM General Builders Inc | B | 2026 | Active |
| Monument Home Services Inc | B | 2003 | Renew by Nov 30, 2026 |
| Moore Home Services | B + C2, C10, C20 +2 | 2019 | Active |
| Mountain Valley Builders | B | 2024 | Active |
| Mullins J K P Construction Inc | B + C36 | 1993 | Active |
| Murphy Jim & Associates | B | 1987 | Active |
| Myers Restaurant Supply LLC | B + D34 | 2012 | Active |
| N B United Construction | B | 2018 | Active |
| N C Construction LLC | B | 2025 | Active |
| N S T Construction Company | B | 2013 | Active |
| Nature Pacific Builders | B | 2021 | Active |
| Nbe Property Restoration | B + C10 | 2019 | Active |
| NCM Builders LLC | B | 2026 | Active |
| Nessco Construction Inc | A, B + C27 | 1999 | Active |
| Nordby Construction Co | A, B | 1979 | Active |
| Nordby Signature Homes Inc | A, B | 2004 | Active |
| Nordby Wine Caves Inc | A, B | 1996 | Active |
| Nordic Contractors Limited | B | 2021 | Active |
| North Bay Cabinets & Installation Inc | B + C6 | 2007 | Active |
| North Bay Flooring Inc | B + C15 | 2020 | Active |
| North Coast Contracting LLC | B2 | 2025 | Active |
| North Coast Solar | B + C46 | 1992 | Active |
| Northern Pacific Power Systems Inc | B + C10 | 2009 | Active |
| Northwest General Engineering LLC | A + HAZ | 2000 | Active |
| Nunley Engineering Inc | A | 2000 | Active |
| O'Rourke Electric Inc | B + C10 | 1993 | Active |
| Ocal | B + C10, C39, C46 | 2013 | Active |
| Ocal Construction & Remodeling Inc | B + C47, D49 | 2021 | Active |
| On Grade General Engineering Inc | A | 2019 | Active |
| Oracle Consulting Inc | B | 2022 | Active |
| Ornelas Construction And Remodeling Inc | B + C39 | 2022 | Active |
| Ortiz Custom Builders Inc | B | 2012 | Active |
| Outside The Box Design & Drafting Services LLC | B | 2023 | Active |
| Over And Under Construction Inc | A | 2026 | Active |
| P & L Specialties | B + D21 | 2002 | Active |
| P B Renovators Inc | B | 2008 | Renew by Dec 31, 2026 |
| Pacific Coast Drilling Company Inc | A + C57 | 1988 | Active |
| Page's Custom Floors | B + C15 | 1992 | Active |
| Palmer J Construction Inc | B | 1994 | Active |
| Parmeter General Engineers & Services Inc | A + C12, D49, HAZ | 2009 | Active |