| Attic Solutions INC | Wolfovich Nir | — | (510) 290 6945 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Attico Building Innovations | Jacob Cain Attia | — | (925) 381 4456 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Attico Enterprise INC | Ron Attia | — | (925) 207 4255 | GC, remodel, ADU | Pleasant Hill · Contra Costa County | — | — |
| Atzun INC | Syed Zulfiqar Rizvi | — | (925) 577 0267 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Audio Video Installations | Dennis George Hoffmann | — | (510) 734 5687 | Other | Rodeo · Contra Costa County | — | — |
| Audio Video Works | Audio Video Works | — | (925) 718 7818 | Other | San Ramon · Contra Costa County | — | — |
| Augustine Fence Company INC | James Ronald Augustine | — | (510) 829 1558 | Other | San Pablo · Contra Costa County | — | — |
| Aura Framing | Aura Framing | — | (510) 759 2458 | Other | Moraga · Contra Costa County | — | — |
| Aura Remodeling | Aura Remodeling | — | (925) 997 4404 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Aussie - Crete | Aussie - Crete | — | (925) 570 8209 | Other | San Ramon · Contra Costa County | — | — |
| Austin Enterprises | Simarro Scott | — | (925) 518 3551 | Other | Antioch · Contra Costa County | — | — |
| Automated Electric | Casey Allen Vandevanter | — | (925) 812 1438 | Electricians | Brentwood · Contra Costa County | — | — |
| Automatic Sprinkler Testing & Inspection Services INC | Octavio Daniel Diaz | — | (707) 645 1782 | Other | Antioch · Contra Costa County | — | — |
| Av Iii INC | Ardell Hubert Iii Visness | — | (925) 567 7037 | Other | Antioch · Contra Costa County | — | — |
| Avalon Rooter | William Aaron Feliciano | — | (510) 399 8744 | Other | Richmond · Contra Costa County | — | — |
| Avalos Roofing | Michael Joseph Avalos | avalosroofing.jay@gmail.com | (510) 758 4646 | Other roofers | Pinole · Contra Costa County | — | — |
| Avant HVAC INC | Oleg Ilyasovich Khafizov | — | (424) 301 1446 | HVAC | Brentwood · Contra Costa County | — | — |
| Avelino Sandoval | Avelino Sandoval | — | (925) 383 3500 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| Avi's Hardwood Floors | Avi's Hardwood Floors | — | (510) 275 3780 | Other | San Pablo · Contra Costa County | — | — |
| Aviv Construction INC | Amir Sharabi | — | (510) 233 4494 | GC, remodel, ADU | Richmond · Contra Costa County | — | — |
| Avlatum Construction | Vladimir Iosifichv Zvidrin | — | (510) 384 7531 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Avon Masonry Construction | Steven Lee Avon | avonconstruction@aol.com | (925) 766 5661 | Other | Antioch · Contra Costa County | — | — |
| Avto Tile Co. | Jejeia Avtandyl | — | (415) 845 6192 | Other | Hercules · Contra Costa County | — | — |
| Award Construction | Noshad Haghighi Ahmad | sunilduttpt6@gmail.com | (925) 787 6880 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Awning Detailers INC | Eric John Leseberg | — | (925) 778 4439 | Other | Antioch · Contra Costa County | — | — |
| Awnings By Infinity | Awnings By Infinity | info@awningsbyinfinity.com | (925) 864 5803 | Other | Concord · Contra Costa County | — | — |
| Axis Demolition | Axis Demolition | — | (415) 637 9378 | Other | Pinole · Contra Costa County | — | — |
| Ay & Fer Electrical | Munoz Giovanny | — | (510) 230 9844 | Electricians | El Sobrante · Contra Costa County | — | — |
| Ayala Builder's And Company INC | Jose Emmanuel Ayalaortiz | — | (415) 260 1025 | GC, remodel, ADU | Richmond · Contra Costa County | — | — |
| Az Builder | Az Builder | — | (925) 812 3150 | GC, remodel, ADU | Pittsburg · Contra Costa County | — | — |
| Azevedo Electric | Brian Philip Jr Azevedo | — | (925) 383 2269 | Electricians | Concord · Contra Costa County | — | — |
| Azim Rafaat | Azim Rafaat | — | (925) 872 3408 | Electricians | Pleasant Hill · Contra Costa County | — | — |
| Aziz Ahmad Azizi | Aziz Ahmad Azizi | — | (925) 499 3868 | HVAC | Concord · Contra Costa County | — | — |
| Azores Construction | Bruce Joseph Alves | — | (925) 522 1263 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Aztec Consultants | Chris Michael Devette | — | (925) 837 1050 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Azteca Stone Works INC | Violeta Gutierrez | — | (925) 432 7791 | Other | Pittsburg · Contra Costa County | — | — |
| Aztech Communications INC | Ernest Jr Padilla | — | (925) 354 6185 | Other | Pittsburg · Contra Costa County | — | — |
| Azzam Construction | Derar Ahmed Elazzam | david@azzamconstruction.com | (510) 435 1513 | GC, remodel, ADU | El Cerrito · Contra Costa County | — | — |
| B & B Floors | B & B Floors | — | (510) 866 8868 | Other | Richmond · Contra Costa County | — | — |
| B & B Glass Aka B & B Windows | Matthew James Brady | — | (925) 765 4626 | Windows, patio, painters | Martinez · Contra Costa County | — | — |