| Albright Painting | Albright Painting | — | (510) 815 4228 | Windows, patio, painters | Rodeo · Contra Costa County | — | — |
| Albright Plumbing | Albright Plumbing | — | (925) 216 8290 | Other | Clayton · Contra Costa County | — | — |
| Albro Electric | Theodore Alexander Albro | — | (341) 242 8132 | Electricians | El Cerrito · Contra Costa County | — | — |
| Alc Construction | Alvarenga Cecilio | acouch@alc-construction.com | (626) 313 7087 | GC, remodel, ADU | Pittsburg · Contra Costa County | — | — |
| Alcala Residential Remodeling | Alcala Residential Remodeling | — | (925) 628 5498 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| Alco Carpentry Co | Victor Manuel Alcocer Cetina | — | (415) 871 9493 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Alco Sheet Metal & Heating INC | Leonard Alfred Farias | — | (510) 432 3028 | HVAC | Alamo · Contra Costa County | — | — |
| Alcon Concrete INC | Murillo Alberto Paredes | asantos@alconconcrete.com | (925) 451-5914 | Other | Pittsburg · Contra Costa County | — | — |
| Alcon INC | Alexandr Pyankov | — | (925) 486 1152 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Alcor Enterprises | Alfred Joseph Jr Accurso | — | (925) 825 5658 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Alcosta Shower Door INC | Ted Bernard Stein | alcostasd@gmail.com | (925) 820 4109 | Other | San Ramon · Contra Costa County | — | — |
| Aldens R Us | Aldens R Us | — | (925) 451 0543 | GC, remodel, ADU | Pleasant Hill · Contra Costa County | — | — |
| Alder Pool & Landscape Co | Donald Lee Vivatson | — | (925) 933 3848 | Windows, patio, painters | Walnut Creek · Contra Costa County | — | — |
| Aldo Painting | Aldo Painting | — | (510) 367 0088 | Windows, patio, painters | El Sobrante · Contra Costa County | — | — |
| Alegria Remodel & Construction Incorporated | Walter Arnold Barillas | — | (707) 641 6135 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Alejandro Gonzalez Reyes | Alejandro Gonzalez Reyes | — | (925) 705 3573 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| Alejandro Romero General Contracting Services | Romero Alejandro | — | (510) 407 3343 | GC, remodel, ADU | Rodeo · Contra Costa County | — | — |
| Aleksandar Kastamanov | Aleksandar Kastamanov | — | (925) 708 7940 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Alex Builder | Alex Builder | — | (510) 776 3563 | GC, remodel, ADU | Richmond · Contra Costa County | — | — |
| Alex Carpet Service INC | Francisco Arriaga | — | (925) 584 0524 | Other | Oakley · Contra Costa County | — | — |
| Alex Concrete | Alex Concrete | goldstandar2025@gmail.com | (510) 734 3136 | Other | Richmond · Contra Costa County | — | — |
| Alex Dongallo Construction | Dongallo Alexander | — | (925) 783 8397 | GC, remodel, ADU | Oakley · Contra Costa County | — | — |
| Alex Kobylik Construction | Kobylik Alex | — | (925) 325 0217 | GC, remodel, ADU | Martinez · Contra Costa County | — | — |
| Alexander Drabkin | Alexander Drabkin | — | (925) 212 0225 | Electricians | Antioch · Contra Costa County | — | — |
| Alexander Toranski | Alexander Toranski | — | (510) 501 2364 | Electricians | Concord · Contra Costa County | — | — |
| Alfa Electric INC | Adan Gustavo Fariasleites | export@alfaelectric.com | (925) 234 5369 | Electricians | Concord · Contra Costa County | — | — |
| Alfa Heating And Cooling | Alfa Heating And Cooling | — | (925) 497 6528 | HVAC | Antioch · Contra Costa County | — | — |
| Alfaro's Construction Services | Johnny Cristian Alfaro | — | (510) 325 3110 | GC, remodel, ADU | El Sobrante · Contra Costa County | — | — |
| Alfonso Baez Painting | Alfonso Baez Painting | — | (925) 305 7724 | Windows, patio, painters | Antioch · Contra Costa County | — | — |
| Alhambra Valley Millworks INC | Kevin Salvatore Balestrieri | — | (415) 722 5442 | Other | Martinez · Contra Costa County | — | — |
| Alisto INC | Evelyn Sevilla | — | (925) 279 5000 | Electricians | Walnut Creek · Contra Costa County | — | — |
| Alive Design & Construction INC | Roshan Rajeewa Habarakada | — | (415) 225 8624 | GC, remodel, ADU | Moraga · Contra Costa County | — | — |
| Alizone Construction | Sadat Lavasani Bozorg Alireza | ali@alizone-construction.com | (408) 449 6469 | GC, remodel, ADU | Pinole · Contra Costa County | — | — |
| All - Pro Glass INC | Robert Donald Landrum | — | (925) 634 8855 | Windows, patio, painters | Brentwood · Contra Costa County | — | — |
| All About Cabinets | Gwen Elizabeth Davis | — | (925) 383 0936 | Other | Martinez · Contra Costa County | — | — |
| All About Construction | Joseph Patrick Phelan | — | (925) 787 3630 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| All About Maintenance | All About Maintenance | — | (925) 768 4994 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| All About Remodels | All About Remodels | — | (925) 381 8891 | GC, remodel, ADU | Martinez · Contra Costa County | — | — |
| All About Service Construction | Lou Mathew Hellman | — | (925) 826 7014 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| All Access Landscape | All Access Landscape | — | (510) 804 4646 | Windows, patio, painters | Richmond · Contra Costa County | — | — |