| Jeff Martinez Construction INC | Jeffrey Al Ii Martinez | martinezj4601@yahoo.com | (925) 584 6535 | GC, remodel, ADU | Oakley · Contra Costa County | — | — |
| Jeff Schwarck Construction | Jefferson B Schwarck | — | (510) 710 0522 | GC, remodel, ADU | Lafayette · Contra Costa County | — | — |
| Jefferson Painting | Jefferson Painting | — | (925) 812 0543 | Windows, patio, painters | Martinez · Contra Costa County | — | — |
| Jeffrey L Peterson Construction | Jeffrey Leonard Peterson | — | (925) 930 7670 | GC, remodel, ADU | Pleasant Hill · Contra Costa County | — | — |
| Jeffrey Young | Jeffrey Young | — | (925) 708 5297 | GC, remodel, ADU | Pittsburg · Contra Costa County | — | — |
| Jens Christian Jensen | Jens Christian Jensen | — | (925) 695 5341 | Other | Brentwood · Contra Costa County | — | — |
| Jensen Mechanical INC | Ryan Mikkel Jensen | — | (925) 240 7154 | HVAC | Oakley · Contra Costa County | — | — |
| Jenuine Painting | Mariana Ascencion Triviso | info@gmail.com | (925) 501 2906 | Windows, patio, painters | Antioch · Contra Costa County | — | — |
| Jeremy Emery | Jeremy Emery | — | (925) 360 5737 | Other | Bay Point · Contra Costa County | — | — |
| Jerome Richardson Painting | Jerome Richardson Painting | — | (510) 223 6105 | Windows, patio, painters | Richmond · Contra Costa County | — | — |
| Jerry Bolla | Jerry Bolla | — | (925) 984 9212 | GC, remodel, ADU | Alamo · Contra Costa County | — | — |
| Jerry Joe Garner | Jerry Joe Garner | — | (510) 714 3787 | GC, remodel, ADU | Moraga · Contra Costa County | — | — |
| Jerry Smith Landscape Services | Gerald Edwin Smith | — | (925) 348 5322 | Windows, patio, painters | Clayton · Contra Costa County | — | — |
| Jess Pool Construction Incorporated | Jeffrey Jay Jess | — | (925) 240 7665 | Pool | Byron · Contra Costa County | — | — |
| Jesse's Concrete | Jesse's Concrete | — | (510) 501 3629 | Other | El Sobrante · Contra Costa County | — | — |
| Jesus Henriquez | Jesus Henriquez | — | (415) 845 8334 | GC, remodel, ADU | El Sobrante · Contra Costa County | — | — |
| Jesus Montes - Gaxiola DBA Montes General Contractor | Montes General Contractor | — | (415) 532 6286 | GC, remodel, ADU | Richmond · Contra Costa County | — | — |
| Jet - HVAC | Jet - HVAC | — | (336) 465-8980 | HVAC | Antioch · Contra Costa County | — | — |
| Jet Tile | Jet Tile | — | (925) 759 8152 | Other | Antioch · Contra Costa County | — | — |
| Jewel Box Woodworks INC | Drew Kerr Smutny | — | (925) 260 4198 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Jf Plumbing | Jf Plumbing | — | (925) 384 6082 | Other | Pittsburg · Contra Costa County | — | — |
| Jfc Construction INC | John Francis Connolly | — | (925) 228 0924 | GC, remodel, ADU | Martinez · Contra Costa County | — | — |
| Jg Construction | Gherasim Joseph | — | (925) 522 6565 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| Jg Construction Builders INC | Garcia Joel | — | (510) 685 9486 | GC, remodel, ADU | El Sobrante · Contra Costa County | — | — |
| Jg Electric | Juan Jose Garcia | — | (925) 435 3964 | Electricians | Walnut Creek · Contra Costa County | — | — |
| Jgg Construction INC | Jose Guillermo Grimaldo | — | (925) 783 4359 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| Jh Home Transformations | Jh Home Transformations | — | (408) 206 5329 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Jhony Salvador Sanchez | Jhony Salvador Sanchez | — | (510) 221 8692 | Other | San Pablo · Contra Costa County | — | — |
| Jian-chon Chu Construction | Chu Jian-chon | — | (510) 302 9295 | GC, remodel, ADU | Pinole · Contra Costa County | — | — |
| Jigsaw Construction INC | Kenton Leroy Rogers | info@jigsaw-construction.com | (510) 282 3376 | GC, remodel, ADU | Lafayette · Contra Costa County | — | — |
| Jikang Zhi | Jikang Zhi | — | (510) 393 5820 | GC, remodel, ADU | El Cerrito · Contra Costa County | — | — |
| Jim Clark Company INC | James Glen Clark | — | (925) 525 1092 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| Jim Davidson Construction | James Paul Davidson | — | (925) 594 0531 | GC, remodel, ADU | Pleasant Hill · Contra Costa County | — | — |
| Jim Freethy Excavating INC | James Lawrence Freethy | — | (925) 855 1440 | Other | Danville · Contra Costa County | — | — |
| Jim Turner Company | James Christian Turner | — | (925) 250 1062 | Windows, patio, painters | Pleasant Hill · Contra Costa County | — | — |
| Jim's Electric LLC | James Arthur Philbrook | — | (925) 351 8474 | Electricians | San Ramon · Contra Costa County | — | — |
| Jim's Heating And Air Conditioning | Jim's Heating And Air Conditioning | — | (925) 783 9417 | HVAC | Oakley · Contra Costa County | — | — |
| Jimmy A Odom General Building Contractor | Jimmy Anthony Odom | — | (925) 628 2486 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| Jimmy John Construction | Jimmy John Perez Montoya | — | (925) 766 3115 | Electricians | Pleasant Hill · Contra Costa County | — | — |
| Jims Air Systems | Jims Air Systems | service@jimsairsystems.com | (925) 584 2634 | HVAC | Oakley · Contra Costa County | — | — |