| Jr Electric And General Contracting INC | John Rilli | — | (925) 864 6953 | Electricians | Concord · Contra Costa County | — | — |
| Jr Painting | Jr Painting | juniorsanabria03@gmail.com | (415) 845 0750 | Windows, patio, painters | Richmond · Contra Costa County | — | — |
| Jr Pavers INC | Sebastiao Marcos Indalecio | — | (510) 200 4940 | Other | Richmond · Contra Costa County | — | — |
| Jr Santos Co | Milton Urias Diaz Lopez | — | (415) 424 2664 | GC, remodel, ADU | Rodeo · Contra Costa County | — | — |
| Jr Windows & Glass Door Installation | Selvin Javier Reyes | info@jrwindowsglassdoorinstallation.com | (415) 860 5881 | Windows, patio, painters | Richmond · Contra Costa County | — | — |
| Jre Construction LLC | Julian Ryan Endonila | — | (925) 323 7839 | GC, remodel, ADU | Martinez · Contra Costa County | — | — |
| Js Tile | Jhony Salvador Sanchez Paz | — | (510) 221 8692 | Other | San Pablo · Contra Costa County | — | — |
| Jsm Construction | Jeffrey Steven Mc Cormick | — | (925) 330 3152 | GC, remodel, ADU | Alamo · Contra Costa County | — | — |
| Jt Painting | Jt Painting | — | (925) 207 0639 | Windows, patio, painters | Pittsburg · Contra Costa County | — | — |
| Jtr Construction Company INC | Thomas Whitton Roy | — | (925) 785 4556 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Juan Infantas Tile Contractor | Juan Infantas Tile Contractor | — | (925) 565 0726 | Other | Antioch · Contra Costa County | — | — |
| Juan Rios Landscaping | Juan Rios Landscaping | ccgs.rios@gmail.com | (925) 642 3543 | Windows, patio, painters | Clayton · Contra Costa County | — | — |
| Juan's Landscape | Juan's Landscape | — | (925) 595 9137 | Windows, patio, painters | Antioch · Contra Costa County | — | — |
| Juarez Framing | Juarez Framing | — | (925) 752 0522 | Other | Bay Point · Contra Costa County | — | — |
| Judieh Plumbing Heating & Air LLC | Mousa Saleh Judieh | — | (925) 261 9313 | HVAC | Pittsburg · Contra Costa County | — | — |
| Julian Haro Renovations | Julian Haro Renovations | jharo.renos@gmail.com | (925) 812 2907 | GC, remodel, ADU | Rodeo · Contra Costa County | — | — |
| Julian Tree Care INC | Julian C Cabrera Ramirez | juliantreecarebids@gmail.com | (510) 256 7009 | Tree | Richmond · Contra Costa County | — | — |
| Julian's Electric And Digital | Julien Seth Steinberg | — | (925) 951 3277 | Electricians | Walnut Creek · Contra Costa County | — | — |
| Julio Guzman | Julio Guzman | — | (415) 902 4914 | Windows, patio, painters | San Pablo · Contra Costa County | — | — |
| Junior's Tree Service INC | Sergio Jesus Gonzalez-Verde | — | (925) 250 2698 | Tree | Pacheco · Contra Costa County | — | — |
| Juniors Construction & Remodeling INC | Linda Esperanza Parra | — | (925) 382 6710 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| Junkcat LLC | Nicholas Michael Arzio | — | (510) 586 5228 | Other | El Cerrito · Contra Costa County | — | — |
| Junked Powered By Veterans INC | Gary Michael Bostick | — | (888) 891 2440 | Other | Concord · Contra Costa County | — | — |
| Junwoong Moon | Junwoong Moon | — | (510) 828 6637 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Just Build INC | Harpreet Simon Dhillon | — | (510) 459 9201 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Just In Time Water Heaters | Just In Time Water Heaters | justintimewaterheaters@gmail.com | (925) 440 9226 | Other | Antioch · Contra Costa County | — | — |
| Just Us Painting | Just Us Painting | — | (510) 632 6260 | Windows, patio, painters | El Sobrante · Contra Costa County | — | — |
| Justice Construction Co | Michael Robert Justice | — | (925) 867 4654 | GC, remodel, ADU | Martinez · Contra Costa County | — | — |
| Justin Aulday | Justin Aulday | — | (510) 815 0931 | Other | Richmond · Contra Costa County | — | — |
| Justin Time Networks | Justin Time Networks | — | (510) 882 6154 | Other | Antioch · Contra Costa County | — | — |
| Jv Construction | Luis Jonatan Vazquez | — | (925) 783 0048 | GC, remodel, ADU | Oakley · Contra Costa County | — | — |
| Jv Services | Jorge Adrian Vazquez Rodriguez | — | (510) 213 2676 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Jvk Painting | Jvk Painting | contact@jvkpainting.com | (925) 231 5308 | Windows, patio, painters | Brentwood · Contra Costa County | — | — |
| Jvlc INC | Jorge Alberto Armenta Gallegos | — | (925) 655 8594 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| Jwj Construction | Jinwoo Jang | — | (925) 389 3591 | GC, remodel, ADU | Danville · Contra Costa County | — | — |
| Jzc Construction INC | Jose Salome Zavala Castillo | — | (510) 520 6975 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| K & B Landscape Services INC | Michael John Kobold | — | (925) 838 1816 | Windows, patio, painters | Concord · Contra Costa County | — | — |
| K & C Construction | Choi Wai Kin | — | (510) 990 2002 | GC, remodel, ADU | El Cerrito · Contra Costa County | — | — |
| K & C General Construction INC | Jose Luis Huaman Juica | — | (925) 445 7241 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| K & G Remodeling | K & G Remodeling | kgremodeling911@gmail.com | (925) 864 1699 | GC, remodel, ADU | Concord · Contra Costa County | — | — |