| 3R Quality Construction | Angelo John Cirrincione | — | (661) 312 6466 | GC, remodel, ADU | Stevenson Ranch · Los Angeles County | — | — |
| 3R Roofing INC | Jesus Alfonso Lopez | — | (530) 554 5117 | Other roofers | Winters · Yolo County | — | — |
| 3R Wood Design INC | Nazaryan Romik | — | (818) 388 1515 | GC, remodel, ADU | Pacoima · Los Angeles County | — | — |
| 3r1 Builders INC | Russell Howard Roben | — | (760) 335 5600 | Electricians | Imperial · Imperial County | — | — |
| 3rd Dimension Construction | Farnaz Margo Halavy Galdjie | — | (310) 266 6395 | GC, remodel, ADU | Venice · Los Angeles County | — | — |
| 3rd Eye Construction | Pezhman Daroovar | — | (818) 397 8502 | GC, remodel, ADU | West Hills · Los Angeles County | — | — |
| 3rd Gen Painting INC | Chandler Allen Padovich | — | (559) 760 4049 | Windows, patio, painters | Fresno · Fresno County | — | — |
| 3rd Gen Pump & Well | 3rd Gen Pump & Well | — | (805) 904 8808 | Other | Pismo Beach · San Luis Obispo County | — | — |
| 3rd Gen Roofing INC | Ryan Harry Crouse | — | (530) 701 2457 | Other roofers | Marysville · Yuba County | — | — |
| 3rd Generation | 3rd Generation | — | (818) 822 1232 | GC, remodel, ADU | Castaic · Los Angeles County | — | — |
| 3rd Generation Builders Team INC | James Frederick Pursel | — | (805) 331 4749 | GC, remodel, ADU | Santa Barbara · Santa Barbara County | — | — |
| 3rd Generation Building And Design | 3rd Generation Building And Design | — | (408) 834 2318 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| 3rd Generation Flooring LLC | Jack Raymond Sickler | — | (559) 258 4848 | Other | Tulare · Tulare County | — | — |
| 3rd Generation Painting | 3rd Generation Painting | — | (925) 382 8997 | Windows, patio, painters | Concord · Contra Costa County | — | — |
| 3rd Generation Roofing | Eric Benjamin Russell | — | (951) 206 2794 | Other roofers | Fontana · San Bernardino County | — | — |
| 3rd Generation Welds INC | Martin Rodriguez Alfaro | — | (661) 344 7590 | Other | Earlimart · Tulare County | — | — |
| 3rd Party Management Services LLC DBA Griffs Construction | Joshua John Griffin | — | (925) 966 4455 | GC, remodel, ADU | Martinez · Contra Costa County | — | — |
| 3rdgen Home Services DBA 3rdgen Heating And Cooling | Devin Rodolfo Osorio | — | (866) 222 7980 | HVAC | Berkeley · Alameda County | — | — |
| 3rs Construction Services INC | Reyes Rodriguez Ricardo | — | (909) 571 4515 | GC, remodel, ADU | Fontana · San Bernardino County | — | — |
| 3sc Electric INC | Samuel Cedric Darilay | — | (408) 505 9517 | Electricians | Sloughhouse · Sacramento County | — | — |
| 3sd | Stewart Shane Schneider | — | (530) 597 6427 | Electricians | Anderson · Shasta County | — | — |
| 3serg Homebuilder INC | Alvaro Martinez | — | (408) 592 1792 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| 3sixty Innovation INC | Mohamad Ismieal Muhsin | — | (858) 304 1093 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 3T Fence LLC | Leah Marie Coffelt | — | (951) 304 9820 | Other | Wildomar · Riverside County | — | — |
| 3ten Stone & Tile INC | Adam Paul Hammett | — | (805) 298 2254 | Other | West Hills · Los Angeles County | — | — |
| 3vi INC | Zara Sophia Faith Younossi | — | (925) 236 0170 | Other | San Ramon · Contra Costa County | — | — |
| 3W Builders INC | William Walter Iv Wilcox | — | (831) 261 8102 | GC, remodel, ADU | Salinas · Monterey County | — | — |
| 3W Construction INC | Raymond Paul Hasch | wweeiihhuuaanngg@gmail.com | (805) 468 9926 | GC, remodel, ADU | Atascadero · San Luis Obispo County | — | — |
| 3wire Refrigeration | Intermediate Holdings Iii LLC Pt | — | (800) 576 0123 | HVAC | Compton · Los Angeles County | — | — |
| 3X Signs | 3X Signs | — | (951) 394 7003 | Other | Riverside · Riverside County | — | — |
| 3Z Electric | Brian Matthew Zumwalt | — | (209) 608 7040 | Electricians | Tracy · San Joaquin County | — | — |
| 4 - Ace Construction | Steven James Cooper | — | (909) 944 5400 | GC, remodel, ADU | Rancho Cucamonga · San Bernardino County | — | — |
| 4 - Ace Construction | Joseph Gilbert Jaramillo | — | (424) 506 0731 | GC, remodel, ADU | Rancho Cucamonga · San Bernardino County | — | — |
| 4 - Clover Landscaping And Maint | Rodriguez Raul | — | (909) 900 3378 | GC, remodel, ADU | Wildomar · Riverside County | — | — |
| 4 - Con Construction Services | Richard John Garabedian | — | (909) 322 4591 | GC, remodel, ADU | Upland · San Bernardino County | — | — |
| 4 - Point Electric Co | Randy Lee Mc Anelly | — | (530) 219 1785 | Electricians | Woodland · Yolo County | — | — |
| 4 Ace Tile | 4 Ace Tile | — | (209) 522 2453 | Other | Modesto · Stanislaus County | — | — |
| 4 Am Systems | 4 Am Systems | — | (707) 773 4699 | Other | Petaluma · Sonoma County | — | — |
| 4 Any Pos | Raul Barbaro Rovira | — | (888) 426 9767 | Other | Hemet · Riverside County | — | — |
| 4 Bay Painting | 4 Bay Painting | — | (510) 710 2442 | Windows, patio, painters | Pleasanton · Alameda County | — | — |