| Arves Mechanical | Arves Mechanical | — | (925) 864 6527 | HVAC | Brentwood · Contra Costa County | — | — |
| As General Contractor | As General Contractor | — | (510) 809 5052 | GC, remodel, ADU | Richmond · Contra Costa County | — | — |
| Asbill Mike Painting Co | Michael John Asbill | — | (925) 766 2426 | Windows, patio, painters | Brentwood · Contra Costa County | — | — |
| Ascend Renovation & Roofing INC | Blake Marshall Thomas | — | (925) 289 7600 | Other roofers | Walnut Creek · Contra Costa County | — | — |
| Ascent Conserve INC | Jason Michael Lesser | — | (925) 406 9050 | HVAC | Danville · Contra Costa County | — | — |
| Ascent Floors | Ascent Floors | — | (925) 487 4027 | Other | Brentwood · Contra Costa County | — | — |
| Ascent INC | Sean Kieran Osborn | — | (844) 627 2368 | HVAC | Danville · Contra Costa County | — | — |
| Ash Bay Construction INC | Rouhani Arash | — | (925) 421 3906 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Ash Havens Construction INC | Ashley Brandon Robe Havens | — | (530) 416 1301 | GC, remodel, ADU | Hercules · Contra Costa County | — | — |
| Asher Brothers Construction INC | Guy Arnold Jennings | — | (925) 406 4776 | GC, remodel, ADU | Danville · Contra Costa County | — | — |
| Ashlar Building Group LLC | Omar Gonzalez | — | (925) 655 7741 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| Ask Jim To Fix It | Ask Jim To Fix It | — | (925) 682 7795 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Asm Mechanical Services | Jesus Alfredo Solano | — | (925) 384 5033 | HVAC | Antioch · Contra Costa County | — | — |
| Aspect Constructions | Aspect Constructions | — | (925) 381 4756 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Aspect Power LLC | Patrick Blaine Gipson | contact@sansoxygen.com | (925) 798 5688 | Electricians | Martinez · Contra Costa County | — | — |
| Aspire Builders | Edward Warren Heathorn | — | (925) 594 6110 | Electricians | Danville · Contra Costa County | — | — |
| Aspire Construction | Thomas Martin Di Mercurio | — | (925) 784 3945 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| Aspire Tree Care | Ricardo Jr Terrazas | — | (925) 448 6884 | Other | Concord · Contra Costa County | — | — |
| Associated Flooring | Associated Flooring | — | (925) 685 9439 | Other | Pacheco · Contra Costa County | — | — |
| Asterix Electric | Milosevic Mija | — | (669) 264 9009 | Electricians | Walnut Creek · Contra Costa County | — | — |
| Astonishing Construction | Jason Michael Cerecedes | — | (925) 765 0901 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Astounding Construction INC | Astounding Construction INC | astoundingconstructioninc@gmail.com | (415) 886-5885 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Astra General Electrical Work INC | Bronislaw Marian Kobierski | — | (925) 250 3886 | Electricians | Antioch · Contra Costa County | — | — |
| Astra Tile Corporation | Vladimir Atanasov Mitev | — | (925) 518 9638 | Other | Lafayette · Contra Costa County | — | — |
| Astro Green Ventures Group LLC | Palmer Albert Hill | — | (925) 217 0311 | Windows, patio, painters | Walnut Creek · Contra Costa County | — | — |
| At Your Door Pool Service INC | Garcia Jermain | info@atyourdoorpoolservice.com | (925) 584 1928 | Pool | Brentwood · Contra Costa County | — | — |
| At&jm Hauling INC DBA A & J Hauling | Andreas Stathis Triplis | — | (888) 907 4285 | GC, remodel, ADU | Orinda · Contra Costa County | — | — |
| Ata Construction And Remodeling | Atamer Coskun | — | (510) 672 1883 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Atc Mechanical LLC | Stiliyan Zvezdelinov Simov | — | (925) 818 8084 | HVAC | Concord · Contra Costa County | — | — |
| Atd Plumbing INC | Jose Armando Torres | — | (925) 305 7679 | Other | Bay Point · Contra Costa County | — | — |
| Athens General Construction LLC | Dimitrios Karapanos | — | (925) 232 4446 | GC, remodel, ADU | Pittsburg · Contra Costa County | — | — |
| Athens Painting & Commercial Coatings INC | John Kochilas | — | (925) 232 4446 | Windows, patio, painters | Pittsburg · Contra Costa County | — | — |
| Ati Traffic Control LLC | Marco Antonio Rodriguez | info@atitrafficcontrol.com | (510) 381 2703 | Other | Brentwood · Contra Costa County | — | — |
| Atic Construction INC | Anthony John Siino | — | (925) 672 8438 | GC, remodel, ADU | Clayton · Contra Costa County | — | — |
| Atlante INC | Adam Ardell Lambert | — | (415) 509 1441 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Atlantis Decorative Coatings | Atlantis Decorative Coatings | — | (650) 906 8801 | Windows, patio, painters | El Cerrito · Contra Costa County | — | — |
| Atlantis H V A C Service | Samuel Sr Arguello | — | (925) 446 1112 | HVAC | Pittsburg · Contra Costa County | — | — |
| Atlantis Pools INC | Robert John Davis | yourpoolman@hotmail.com | (925) 736 0447 | Pool | Danville · Contra Costa County | — | — |
| Atlas Pavers Co | Candido Otavio Pires Da Sr Silva | — | (925) 852 7438 | Other | Concord · Contra Costa County | — | — |
| Atlas Tree Service INC | William Wayne Lloyd | atlastreeservice@atlastreeservice.com | (925) 687 3631 | Tree | Pleasant Hill · Contra Costa County | — | — |