| One Call Construction And Remodeling INC | Randy Shane Crick | — | (408) 807 9954 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| One Call Services | One Call Services | — | (408) 479-6597 | Restoration | Santa Clara · Santa Clara County | — | — |
| One Cloud General Construction | Carlos Gomez Lizarraga | — | (408) 209 3357 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| One Day Complete Repipe INC | Jose Luis Mendez | — | (408) 603 0554 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| One Day Doors & Closets Of Bay Area | One Day Doors & Closets Of Bay Area | — | (650) 864-8835 | Windows, patio, painters | Santa Clara · Santa Clara County | — | — |
| One Hand Construction | Atias Michael | — | (888) 808 0803 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| One Piece Painting | One Piece Painting | — | (408) 836 0489 | Windows, patio, painters | Campbell · Santa Clara County | — | — |
| One Play Construction Developer | Luis Ivan Canseco Ramirez | — | (408) 472 5146 | GC, remodel, ADU | Los Altos · Santa Clara County | — | — |
| One Pro Concrete INC | Carlos Alberto Jr Pintos | — | (408) 426 6169 | Other | San Jose · Santa Clara County | — | — |
| One Source General Contracting Services INC | Aldo Cesar Castellanos Contreras | — | (408) 838 5543 | GC, remodel, ADU | Gilroy · Santa Clara County | — | — |
| One Stop Garage Doors And Gates INC | Shimon Ohayon | — | (408) 318 1227 | Other | San Jose · Santa Clara County | — | — |
| One Stop INC | Joseph Rodolfo Vergara | — | (408) 848 4441 | GC, remodel, ADU | Gilroy · Santa Clara County | — | — |
| One Time Development Company | Ly Minh | — | (408) 640 5450 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| One Way Garage Door Co | Donald Joseph Foley | — | (408) 391 9382 | Other | Milpitas · Santa Clara County | — | — |
| One Way Painting | One Way Painting | — | (408) 313 5662 | Windows, patio, painters | San Jose · Santa Clara County | — | — |
| One Workplace L Ferrari LLC | Christopher Michael Park | — | (669) 800 2500 | Other | Santa Clara · Santa Clara County | — | — |
| One-up Builders | Rickie Hogan | — | (408) 312 7238 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| One10 | Alex Saulus | — | (408) 471 6741 | Electricians | Morgan Hill · Santa Clara County | — | — |
| Oneto Construction & Woodworks | David Lawrence Oneto | — | (530) 386 6631 | GC, remodel, ADU | Campbell · Santa Clara County | — | — |
| Onit Remodeling | Nam Tran Minh Doan | — | (669) 255 1963 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| Only Up Construction INC | Haro Juan De | — | (408) 313 0011 | Electricians | Gilroy · Santa Clara County | — | — |
| Onpoint Construction | David Mekhail Gewargis | — | (408) 472 1519 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| Onward Construction | Aaron Michael Sommese | info@onwardbuilds.com | (408) 332 1508 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| Onward Electric LLC | Cory Noel Stevens | — | (205) 393 3814 | Electricians | San Jose · Santa Clara County | — | — |
| Open Space Builders INC | Don Xiangdong Su | — | (650) 680 6803 | GC, remodel, ADU | Los Altos · Santa Clara County | — | — |
| Opi Commercial Builders INC | Jonathan Mark Persing | — | (408) 377 4800 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| Optimal Earthwork And Grading INC | Alexis Paul Chavez | — | (408) 603 3805 | Other | San Jose · Santa Clara County | — | — |
| Optimum Pools INC | Optimum Pools INC | — | (669) 667-6657 | Pool | Sunnyvale · Santa Clara County | — | — |
| Opulands Landscape Design & Construction | Dongen Steven Van | — | (800) 239 6658 | Windows, patio, painters | Campbell · Santa Clara County | — | — |
| Opulent Bay Homes INC | Abel Fuentes | — | (650) 284 8708 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| Or Homes | Mandeep Singh Bhogal | — | (408) 357 3043 | GC, remodel, ADU | Cupertino · Santa Clara County | — | — |
| Oracle Construction INC | Julio Adan Caballero | — | (408) 661 4864 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| Orange Home Builders INC | Eyal Carmel | — | (413) 539 4690 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |
| Orbe Builders INC | Angel De Jesus Gomez Orbe | — | (669) 208 5424 | GC, remodel, ADU | Milpitas · Santa Clara County | — | — |
| Orbis Electrical Works | Ivaylo Todorov Barbolov | — | (650) 271 7991 | Electricians | San Jose · Santa Clara County | — | — |
| Orchard Bay Landscaping LLC | Jaime Juan Manuel Rivera | orchardbaylandscaping@gmail.com | (699) 258 7836 | Windows, patio, painters | Gilroy · Santa Clara County | — | — |
| Orchard City Builders INC | Todd William Zeman | — | (408) 374 2476 | Electricians | Campbell · Santa Clara County | — | — |
| Orchard City Electric | Peter Duke Torrisi | — | (408) 478 0034 | Electricians | Campbell · Santa Clara County | — | — |
| Orchard City Lock & Safe INC | David Vlamis | — | (408) 879 9840 | Other | Campbell · Santa Clara County | — | — |
| Orchard Valley Construction | Antonio Rodriguez Perez | — | (408) 813 0896 | GC, remodel, ADU | San Jose · Santa Clara County | — | — |