| Levon Construction Group Inc | A | 2025 | Active |
| Lewis Carl Co | B | 1986 | Active |
| Lincoln Construction Corporation | A | 2013 | Active |
| Lindley Fire | A + C10, C16, C34 | 2018 | Active |
| Linzaga Construction Inc | B | 2020 | Active |
| LLT Construction Inc | A, B | 2024 | Active |
| Lonestar Construction Inc | B + C29, C35, C39 +1 | 2011 | Active |
| Lopez Ortiz General Contractor | B | 2025 | Active |
| Lovineh Design And Construction Group | B | 2025 | Active |
| LTP Construction Inc | B + D28 | 2026 | Active |
| Lucky Construction & Painting Inc | B + C33 | 2010 | Active |
| Luxury Bath Designs Of Orange County Inc | B | 2025 | Active |
| LW Engineering | A | 2026 | Active |
| Lyle Parks Jr Construction A California Partnership | B | 2005 | Active |
| M & D Maintenance Repair | B | 2009 | Active |
| M C C Construction & Restoration Services Inc | B + C33 | 1997 | Active |
| M P South Inc | B | 1979 | Active |
| M T L Construction Services Inc | B | 2006 | Active |
| Maga Project Developers | B | 2025 | Active |
| Maintenance And Restoration Inc | B | 2024 | Active |
| Malco Services Inc | B | 2012 | Active |
| Mayeda Tim Inc | B | 2005 | Active |
| McCollom Concrete & Masonry Inc | B + C8, C29, C53 | 2021 | Active |
| Mendoza V Construction Inc | B | 1999 | Active |
| Mesa Garage Doors | B + D28 | 1999 | Active |
| Methodical Home Improvement & Remodeling | B2 | 2024 | Active |
| MG Developer's Inc | B + C20, C36 | 2012 | Active |
| Micropro Construction Inc | B | 2025 | Active |
| Millenium Design And Services Inc | B + C54 | 2022 | Active |
| Millennial Property Maintenance Inc | B | 2025 | Active |
| Millennium Stonewurks | B + C54 | 2007 | Active |
| Miller H L Inc | B + C6, C33, C39 | 1979 | Active |
| Millworksoc | B + C6 | 2016 | Renew by Nov 30, 2026 |
| Mirage Builders Inc | B + C6, C9, C33 +1 | 1992 | Active |
| Miranda Crestwood Construction | B | 2022 | Active |
| Mission Development Consultants | B | 1986 | Renew by Dec 31, 2026 |
| ML Development | B | 2025 | Active |
| Mlife Builder Inc | B + C10 | 2020 | Active |
| Modern Creation - General Building & Plumbing | B + C54 | 2020 | Active |
| Modern Metal Framing & Drywall Inc | B + C2, C9 | 2021 | Active |
| Modern Vista Construction Inc | B | 2018 | Active |
| Morrison Construction & Millwork Inc | B | 1990 | Active |
| Mr Rocco's Plumbing | B + C36, C42 | 2015 | Active |
| Mr Rooter Plumbing | B + C36, C42 | 1999 | Active |
| Murray Construction Services | B | 2012 | Active |
| Myers R M Corporation | B + ASB, C21, C22 +1 | 1997 | Active |
| N F Brothers Construction Inc | B | 2023 | Active |
| N F J Contractors Inc | A, B + C33 | 2024 | Active |
| N K S Mechanical Contracting Inc | B + C20 | 2005 | Active |
| Natural Elements Construction Inc | B | 2017 | Active |
| Navo Builders Inc | B | 2024 | Active |
| Navpoint LLC | B + C43 | 2021 | Active |
| Nazz Cali Construction_inc | B | 2024 | Active |
| Nazz Construction Inc | B | 2015 | Active |
| Nba Electric | B + C10 | 2026 | Active |
| NCT Construction Inc | B | 2022 | Active |
| Neos Construction | B | 2017 | Active |
| New Century Door Inc | B | 1997 | Active |
| New Era Building Maintenance | B | 2026 | Active |
| New Vision United Corporation | B | 2021 | Active |
| Nexlevel Construction & Renovations Inc | B | 2024 | Renew by Dec 31, 2026 |
| Next Door Roofing Inc | B + C39 | 2021 | Active |
| Next Generation Contractors Inc | B | 2015 | Active |
| Niccon Enterprises Inc | B | 1977 | Active |
| NNX Construction Inc | B | 2021 | Active |
| No Limit Construction | B | 2008 | Active |
| Nois Construction Inc | B | 2019 | Active |
| Oakland Company Inc | B + C29, D34 | 2004 | Active |
| Oakwest Services Inc | A, B + C27 | 2013 | Active |
| Oc Side Construction And Design Inc | B | 2023 | Active |
| Ocbs Inc | B | 1987 | Active |
| Olvera G Construction Inc | B | 2017 | Active |
| Onda Construction Inc | B | 2025 | Active |
| One Step Ahead Construction Inc | B + C33, D12 | 2022 | Active |
| Orange County Asphalt Inc | A | 1998 | Active |
| Orange County Construction Inc | B | 2010 | Active |
| Orange County Erectors Inc | B + C51 | 1977 | Active |
| Orange County Property Services Inc | B + C7, C10, C13 | 2008 | Active |
| Original Mr Cabinet Care The | B + C6, D12 | 1991 | Active |
| Outside The Lines Inc | A + C53 | 2007 | Active |
| Overwatch Construction Management | B | 2020 | Active |
| P A Commercial Construction Inc | B + C6 | 2007 | Active |
| P C M Construction Inc | B | 2008 | Active |
| P D C Interiors | B | 1982 | Renew by Nov 30, 2026 |
| Pacific Construction Group | B | 1997 | Active |
| Pacific Grade Engineering Inc | A | 2008 | Active |
| Pacific Interior Electric | B + C10 | 1995 | Active |
| Pacific States Utility Company | A, B + C10, C36 | 1976 | Active |
| Pacific Stone USA LLC | B + C10, C54 | 2026 | Active |
| Pacific Wall Systems Inc | B + C2, C9 | 2001 | Active |
| Parks Lyle Jr Inc | B | 1970 | Active |
| Parkwest General Contractors | B + C9, D50 | 2007 | Active |
| Patino Incorporated | B | 2022 | Active |
| Paulus Engineering Inc | A + HAZ | 1996 | Active |
| Paulus R F Inc | A + HAZ | 1983 | Active |
| PBC Companies | B + C8, C29 | 1989 | Active |
| Pedraza Construction Company | B | 2024 | Active |
| Penhall Company | A, B + ASB, C21, D06 +1 | 1989 | Active |
| Perez D F Construction Inc | B + C8 | 1980 | Active |
| Pinault R D Company | B | 1984 | Active |