| San Fernando Transit Constructors | A | 2022 | Active |
| Santillan Construction Services Inc | B | 2024 | Active |
| Saver Building Solutions | B | 2022 | Active |
| Sbko LLC | B | 2025 | Active |
| SBR Engineering Consultants Inc | B | 2011 | Active |
| SC Construction & Restoration Inc | B | 2026 | Active |
| SC Construction Services Corp | B | 2024 | Active |
| SC Constructors | A | 2025 | Active |
| Schaefer Building Company LLC | B | 2023 | Active |
| Schuler Constructors Inc | A | 2014 | Active |
| Schwartz Construction | A, B + C17 | 1991 | Active |
| Semna | A + C10 | 2021 | Active |
| Serafin's Engineering Corp | A | 2018 | Active |
| Servicemaster Recovery Services By 24/7/365 | B | 2026 | Active |
| Servicemaster Restoration By WFDR | B | 2014 | Active |
| Servpro Of West Riverside City | B + D64 | 2019 | Active |
| Servpro Of Woodcrest El Cerrito/Lake Matthews/Lake Elsinor/Perris | B | 2018 | Renew by Nov 30, 2026 |
| Sevco Restoration Inc | B | 2020 | Active |
| Sevilla Construction Inc | B | 2016 | Renew by Nov 30, 2026 |
| Shaco Construction Inc | B | 2024 | Active |
| Sharp Electrical Services | B + C10, C39, C47 | 2019 | Active |
| Sherwood Construction & Electric Inc | B + C10 | 1984 | Active |
| Sidra Group Inc | A + C13, C51 | 2011 | Active |
| Sigma One Construction Inc | A + C10 | 2024 | Active |
| Signal Fluid Solutions Inc | B | 2014 | Active |
| Sirius Mechanical Inc | B + C20 | 2004 | Active |
| Skanska - Coffman A Joint Venture | A | 2024 | Active |
| Skanska - Rados Expo 2 Joint Venture | A, B | 2010 | Active |
| Skanska - Traylor - Shea A Joint Venture | A, B + C10, HAZ | 2013 | Active |
| Skanska Constructors | A, B + C51 | 2012 | Active |
| Skanska Sully - Miller A Joint Venture | A | 2024 | Active |
| Skanska USA Civil West California District Inc | A + C10, C34, HAZ | 1953 | Active |
| Skanska-Cec Joint Venture | A | 2023 | Active |
| Skanska-Coffman A Joint Venture II | A + HAZ | 2025 | Active |
| Skanska-Flatiron A Joint Venture | A | 2025 | Active |
| Skanska-Stacy And Witbeck A Joint Venture | A | 2013 | Active |
| Sky Maintenance & Repair Inc | B | 2011 | Active |
| Skyline Construction | B + C10, C20 | 2015 | Active |
| Skyline Industries & Environmental Services | B + C21, C22, D63 | 2022 | Active |
| Smile Seekers Development Inc | B | 2011 | Active |
| So Cal Door & Trim Inc | B | 2018 | Active |
| So Cal Tile Pro's | B2 + C54 | 2023 | Active |
| Sol Construction Inc | A | 2002 | Active |
| Solarcon Inc | B + C10, C17, C20 +2 | 2015 | Active |
| South County Interiors Inc | B | 2016 | Active |
| South Pacific General Contracting Corp | B | 2020 | Active |
| Southwest General Engineering Inc | A | 1999 | Active |
| Spartan Installations Corp | B + C6 | 2024 | Active |
| Specialized Coatings & Waterproofing LLC | B | 2023 | Active |
| Specialized Environmental Technologies Corporation | A + HAZ | 2025 | Active |
| Spsa Incorporated | B | 2018 | Active |
| Square Level Remodeling Inc | B2 | 2024 | Active |
| SRC Homes Inc | B | 2020 | Active |
| SSH Joint Venture | A + HAZ | 2025 | Active |
| Stainless Fixtures Inc | B + C38, C43 | 1998 | Active |
| Statewide General Contractors Inc | B | 2009 | Active |
| Steimer Construction Inc | B | 1993 | Active |
| Stellar Energy LLC | B + C10 | 2024 | Active |
| Stilwell Construction Inc | A, B | 1991 | Active |
| STMG Engineering | A | 2026 | Active |
| Storm Guard Construction Inc | B + C39 | 2020 | Active |
| Strength Inc | A, B + C8 | 2002 | Active |
| Stronghold Power Systems Inc | A, B + C10 | 2019 | Active |
| Sun Boss Rooms & Baths | B + D03 | 1975 | Active |
| Sun Tzu Inc | B | 2026 | Active |
| Sunfire Construction Inc | B + D12 | 2021 | Active |
| Sunnyslope Construction Inc | B + C33 | 2006 | Active |
| Sunstate Home Improvements Inc | B + C27 | 2010 | Active |
| Superior Concrete Construction | B + C8 | 1986 | Active |
| Superior Hot Tapping Services Inc | A | 2020 | Active |
| Superior West Plumbing | B + C36 | 2016 | Active |
| Swanson Construction Development Inc | B | 2014 | Active |
| Syntech Roofing And Waterproofing | B + C39 | 2023 | Active |
| T A Rivard Inc | A + ASB, C34, C42 | 1979 | Active |
| T And S Development Inc | B | 2025 | Active |
| T P Remodeling Inc | B | 1993 | Active |
| T V R Construction Engineering LLC | A, B | 2020 | Active |
| Tank - Tek Environmental Corporation | A | 2002 | Active |
| Tavaglione Construction & Development Inc | A, B + C8, C27 | 1972 | Active |
| Teco Construction Inc | B | 1996 | Active |
| Ten-Pac Construction Corp | B | 2021 | Active |
| The Colbart Company | B + C20, C36 | 2005 | Active |
| The Restoration Doctors Inc | B | 2026 | Active |
| Thomson Rick Construction Company Inc | B | 2014 | Active |
| Tilden-Coil Constructors Inc | A, B | 1962 | Active |
| Tli Construction Inc | B | 2007 | Active |
| TMC Construction Inc | A | 2025 | Active |
| TMP Services Inc | B | 1994 | Active |
| Tomahawk Builders Inc | B + C5 | 2004 | Active |
| Tony Reed Construction Inc | B + C29 | 2015 | Active |
| Top Quality Framing | B + C5 | 2013 | Active |
| Trending Construction | B | 2024 | Active |
| Trinidad Construction Inc | B | 2018 | Active |
| Trinity Fence Company | A + C13 | 2020 | Active |
| True Reality Development Corp | B + C15, D12 | 2025 | Active |
| True Vision Construction Inc | B | 2025 | Active |
| Trueline | A + ASB, C32 | 1993 | Active |
| Truly Creative Development LLC | B | 2024 | Active |
| Twenty20 Construction Consulting Inc | B | 2021 | Active |
| Ultimate Construction | B + C53 | 2008 | Active |