| Woodruff Roofing | Don James Woodruff | — | (209) 481 6088 | Other roofers | Brentwood · Contra Costa County | — | — |
| Woods Welding | Woods Welding | — | (925) 470 6995 | Other | Antioch · Contra Costa County | — | — |
| Workshop INC | Christian William Wiedemann | — | (415) 794 3394 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| World Concepts | World Concepts | — | (510) 599 3044 | GC, remodel, ADU | Lafayette · Contra Costa County | — | — |
| World Of Sound & Vision INC | Kevin Michael Musante | — | (925) 820 4900 | Electricians | Pleasant Hill · Contra Costa County | — | — |
| Worthy Remodeling And Renovations | Stephanie Warren | — | (925) 457 5671 | GC, remodel, ADU | Alamo · Contra Costa County | — | — |
| Woznak Construction | Brian Paul Woznak | — | (925) 639 1000 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Ws Renovation INC | Catherine Stoupas | — | (925) 886 2073 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Xact Pool & Spa | Xact Pool & Spa | — | (925) 827 9228 | Pool | Concord · Contra Costa County | — | — |
| Xas Painting INC | Marissa Isabel Hernandez | — | (925) 437 8302 | Windows, patio, painters | Antioch · Contra Costa County | — | — |
| Xavier Electric | Xavier Portillo Gonzales | — | (925) 818 6639 | Electricians | Bay Point · Contra Costa County | — | — |
| Xcel Heating And Air Conditioning INC | Anupinder Singh Khattra | — | (925) 433 6400 | HVAC | Lafayette · Contra Costa County | — | — |
| Xel - Woods Fine Hardwood Floors | Evaristo-malvaez Enrique | — | (510) 921 0197 | Other | Concord · Contra Costa County | — | — |
| Xin Feng INC | Xin Jie Feng | — | (415) 525 7335 | Other | Pinole · Contra Costa County | — | — |
| Xp Squared Construction & Landscaping | Paredes Genaro | — | (650) 201 2254 | GC, remodel, ADU | San Pablo · Contra Costa County | — | — |
| Xtreme Electric | David Louis Verhoek | dave.xtremeelectric@gmail.com | (925) 708 4154 | Electricians | Danville · Contra Costa County | — | — |
| Xtreme Scaffolding | Xtreme Scaffolding | — | (925) 957 6642 | Other | Martinez · Contra Costa County | — | — |
| Xu Liqing | Xu Liqing | — | (510) 328 5777 | GC, remodel, ADU | Danville · Contra Costa County | — | — |
| Xue Chen | Xue Chen | — | (305) 215 9157 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Xuehui Li | Xuehui Li | — | (925) 900 8166 | GC, remodel, ADU | Danville · Contra Costa County | — | — |
| Y Group Remodeling INC | Ohayon Yarin | info@ygroupremodeling.com | (510) 899 1053 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Y W Electrical Co INC | William Yiu Wai Yung | — | (510) 915 1698 | Electricians | Richmond · Contra Costa County | — | — |
| Y.o.d.a Construction | Ejraei Seisan Arash | — | (925) 260 1877 | GC, remodel, ADU | Martinez · Contra Costa County | — | — |
| Yarbrough Construction | Scott Michael Yarbrough | — | (925) 787 7607 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Yard Assistant LLC | Christopher Robert Miller | — | (925) 471 2625 | Windows, patio, painters | Concord · Contra Costa County | — | — |
| Yardformz Interlocking Pavers | De Sousa Melo Taynara Bueno | — | (341) 600 9584 | Other | Richmond · Contra Costa County | — | — |
| Yaseth Silva Finish Carpenter INC | Emir Yaseth Silva Arbizu | — | (786) 881 1661 | Other | Concord · Contra Costa County | — | — |
| Yepez Construction | Yepez Ramirez Abraham | — | (630) 486 4283 | Other roofers | Martinez · Contra Costa County | — | — |
| Yes Flooring Contractors | Mark Emerson Yeadaker | — | (650) 290 4432 | Other | Concord · Contra Costa County | — | — |
| Yl Builders INC | Young Chi Lu | tstephens@ylbuilders.com | (415) 867 2232 | GC, remodel, ADU | San Pablo · Contra Costa County | — | — |
| Ynot Heating And Air | Ynot Heating And Air | — | (925) 250 4899 | HVAC | Antioch · Contra Costa County | — | — |
| You Name It Construction Services | Thomas Anthony Jr Mazza | — | (925) 209 3524 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| Young & Burton INC | Michael Gerald Burton | — | (925) 820 4953 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Young Electrical Services | John Edward Iii Young | — | (925) 595 0438 | Electricians | Walnut Creek · Contra Costa County | — | — |
| Young's Consulting | Young's Consulting | — | (925) 783 6543 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| Younger Brothers Builders | Campbell Steven Younger | — | (925) 289 8145 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Yt Locksmith | Yoshiel Hagbi | hello@locksmith.example | (925) 440 0476 | Other | Concord · Contra Costa County | — | — |
| Yurkevich Build Co | Gennadiy Sergeyevich Yurkevich | — | (510) 677 9670 | GC, remodel, ADU | Pacheco · Contra Costa County | — | — |
| Yutronics Systems | Yutronics Systems | — | (925) 388 8166 | Other | Concord · Contra Costa County | — | — |
| Yv Construction | Sharma Neil | — | (925) 666 5057 | GC, remodel, ADU | Pittsburg · Contra Costa County | — | — |