| 2l2a Painting | Ludwing Edgar Barrios | — | (909) 632 5680 | Windows, patio, painters | Lake Elsinore · Riverside County | — | — |
| 2nd Chance Backflow Solutions | 2nd Chance Backflow Solutions | — | (909) 477 0018 | Other | Jurupa Valley · Riverside County | — | — |
| 2s2g Contracting INC | Michael Anthony Harrod | — | (714) 602 7855 | Other | Corona · Riverside County | — | — |
| 3 Bro's Roofing INC | Cesar Leonel Gomez Sarmiento | info@brosroofing.com | (905) 516-9515 | Other roofers | Quail Valley · Riverside County | — | — |
| 3 N 1 Landscape | 3 N 1 Landscape | — | (760) 851 4972 | Windows, patio, painters | Thousand Palms · Riverside County | — | — |
| 3 Palms Pool And Spa | 3 Palms Pool And Spa | — | (951) 722 6002 | Pool | Moreno Valley · Riverside County | — | — |
| 3 Sixty-five Framers | Cordero Jose Alfredo Blanco | — | (951) 642 1999 | Other | Perris · Riverside County | — | — |
| 3 Sons Plumbing INC | Joel Mark Levine | — | (760) 567 1570 | Other | La Quinta · Riverside County | — | — |
| 311 Construction General Contractor | Perez Mario Silva | — | (951) 282 5196 | GC, remodel, ADU | Hemet · Riverside County | — | — |
| 33 Andrade Enterprises INC | Nicholas Francisco Andrade | — | (951) 634 2111 | GC, remodel, ADU | Temecula · Riverside County | — | — |
| 357 Waterproofing INC | Fermin Santana Sr Lopez | — | (714) 329 6622 | Other | Corona · Riverside County | — | — |
| 360 Construction | George Lewis Chaney | — | (760) 218 0778 | GC, remodel, ADU | Palm Springs · Riverside County | — | — |
| 360 Construction & Remodeling INC | Victor Pinedo | — | (310) 341 6000 | GC, remodel, ADU | Moreno Valley · Riverside County | — | — |
| 360 Glass & Mirrors | 360 Glass & Mirrors | — | (949) 680 0908 | Windows, patio, painters | Wildomar · Riverside County | — | — |
| 395 Engineering | Eric Magana | — | (951) 529 1204 | Other | Jurupa Valley · Riverside County | — | — |
| 3C Construction INC | Juan Carlos Acosta | — | (626) 625 4626 | GC, remodel, ADU | Mira Loma · Riverside County | — | — |
| 3D Floors | Ulises Daniel Alvarado Cuenca | — | (909) 758 3042 | Other | Moreno Valley · Riverside County | — | — |
| 3G Plumbing INC | Fuentes Daniel Casillas | — | (760) 234 2494 | Other | Indio · Riverside County | — | — |
| 3gen Contractors | Armando Velazquez | — | (909) 631 4355 | GC, remodel, ADU | Riverside · Riverside County | — | — |
| 3gm Builders | Sergio Madrigal | — | (949) 705 9059 | GC, remodel, ADU | Corona · Riverside County | — | — |
| 3M Pools | Mario Mariscal Machaen | — | (909) 630 4300 | Pool | Jurupa Valley · Riverside County | — | — |
| 3P Landscape | Jose Manuel Cruz | — | (951) 454 2276 | Electricians | Menifee · Riverside County | — | — |
| 3R Electric | Bassam Ali Elhambra | — | (714) 768 2787 | Electricians | Riverside · Riverside County | — | — |
| 3T Fence LLC | Leah Marie Coffelt | — | (951) 304 9820 | Other | Wildomar · Riverside County | — | — |
| 3X Signs | 3X Signs | — | (951) 394 7003 | Other | Riverside · Riverside County | — | — |
| 4 - Clover Landscaping And Maint | Rodriguez Raul | — | (909) 900 3378 | GC, remodel, ADU | Wildomar · Riverside County | — | — |
| 4 Any Pos | Raul Barbaro Rovira | — | (888) 426 9767 | Other | Hemet · Riverside County | — | — |
| 4 Com Incorporated | Francisco Cruz Paz | — | (951) 742 8006 | Other | Riverside · Riverside County | — | — |
| 4 Corners INC | Ronald Arthur Johnson | — | (818) 855 6722 | GC, remodel, ADU | Menifee · Riverside County | — | — |
| 4 Point Contracting INC | Jazzet Husai Castellanos Morales | — | (951) 254 8494 | GC, remodel, ADU | Corona · Riverside County | — | — |
| 4 S General Engineering INC | Jon Talmadge Stone | — | (951) 733 8888 | Other | Temecula · Riverside County | — | — |
| 4 T Plumbing Co | Thomas Frederick Long | — | (951) 235 2648 | Other | Riverside · Riverside County | — | — |
| 4 West Pipeline INC | Herrera Hernandez Roberto | — | (951) 244 0002 | Other | Canyon Lake · Riverside County | — | — |
| 4.0 Electric INC | Matthew Mark Padilla | — | (951) 249 1176 | Electricians | Murrieta · Riverside County | — | — |
| 40 Plus Home Improvement INC | Sun Yuan | — | (626) 525 1861 | HVAC | Corona · Riverside County | — | — |
| 4K Pools | 4K Pools | — | (951) 522 3816 | Pool | Menifee · Riverside County | — | — |
| 4K Roofing | Jason Palmadge Stone | 4kroofing.socal@gmail.com | (951) 396 5419 | Other roofers | Eastvale · Riverside County | — | — |
| 5 Star Builder | 5 Star Builder | — | (949) 678 0763 | GC, remodel, ADU | Lake Elsinore · Riverside County | — | — |
| 5 Star Flooring INC | Dustin Lee Garrett | — | (951) 616 9373 | Other | Canyon Lake · Riverside County | — | — |
| 5 Star General Construction | Warren Frederick Jr Smith | — | (909) 720 8482 | GC, remodel, ADU | Norco · Riverside County | — | — |