| Jin188 Construction | John Yee | — | (415) 812 4076 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Jisatech Wireless INC | Juan Roberto Soto Romano | — | (650) 630 8395 | Other | Hercules · Contra Costa County | — | — |
| Jj | Kimberly Ruby Ruedas-alvarado | — | (310) 948 3838 | Other | Antioch · Contra Costa County | — | — |
| Jj Construction | Jorge Alan Trejo Hernandez | — | (925) 681 8454 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Jj's Fine Painting INC | Javier Jair Sr Davila Huizar | — | (510) 998 6021 | Windows, patio, painters | San Pablo · Contra Costa County | — | — |
| Jjp Electric INC | Jose Agustin Jimenez | — | (510) 815 4898 | Electricians | Pittsburg · Contra Costa County | — | — |
| Jl Landscaping LLC | Jose Angel Loza | — | (925) 354 0656 | Windows, patio, painters | Antioch · Contra Costa County | — | — |
| Jld Electric INC | Jeffrey Lester Doolittle | — | (510) 409 3776 | Electricians | Concord · Contra Costa County | — | — |
| Jlh Legacy Flooring | Jose Luis Hernandez | — | (925) 405 2328 | Other | Concord · Contra Costa County | — | — |
| Jlima Demolition Services | Jarbas Ferreira De Lima | — | (510) 837 7972 | Other | Richmond · Contra Costa County | — | — |
| Jll Electric INC | Joshua Leonard Lopez | — | (925) 695 4993 | Electricians | Martinez · Contra Costa County | — | — |
| Jm Outdoor Solution INC | Simeon De Jesus Ixcoy Morales | — | (510) 821 5295 | Windows, patio, painters | Richmond · Contra Costa County | — | — |
| Jmk Construction Projects | Justin Moore Kirby | — | (925) 395 1465 | GC, remodel, ADU | Pleasant Hill · Contra Costa County | — | — |
| Jms Development | Jms Development | — | (925) 580 7963 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Jn Landscaper | Jn Landscaper | — | (925) 628 2503 | Windows, patio, painters | Pittsburg · Contra Costa County | — | — |
| Jnb Construction Company | Jorge Nicholas Beverina | — | (510) 290 9056 | GC, remodel, ADU | Pinole · Contra Costa County | — | — |
| Jnc Plumbing INC | Jose Guadalupe Comparan Campos | — | (415) 571 4641 | Other | El Sobrante · Contra Costa County | — | — |
| Jnj Rooter And Plumbing LLC | Jesus Arturo Renteria | — | (925) 309 9083 | Other | Concord · Contra Costa County | — | — |
| Joachim Services | Christopher Lee Joachim | — | (925) 812 1381 | Electricians | Martinez · Contra Costa County | — | — |
| Jobon Heating And Air Conditioning | Juan Miguel Munoz Arreola | — | (415) 774 6094 | HVAC | Pleasant Hill · Contra Costa County | — | — |
| Joe A Callaway | Joe A Callaway | — | (925) 413 0523 | Electricians | Danville · Contra Costa County | — | — |
| Joe Farrell Paving & Grading INC El Sobrante Sewer Repair | Joseph Scott Farrell | — | (510) 593 3742 | Other | El Sobrante · Contra Costa County | — | — |
| Joe Matta Construction | Joe Edward Matta | — | (925) 270 5899 | GC, remodel, ADU | Martinez · Contra Costa County | — | — |
| Joe O Construction | Joseph Michael Olszewski | — | (925) 497 4466 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Joe Santos Painting | Joe Santos Painting | — | (925) 567 6072 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Joe Walsh Custom Drywall | Joe Walsh Custom Drywall | — | (925) 930 8588 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Joe's Gardening & Landscape Company | Joseph Allen Domon | — | (510) 219 5516 | Windows, patio, painters | Richmond · Contra Costa County | — | — |
| Joe's Home Improvement | Joe's Home Improvement | — | (925) 451 1703 | GC, remodel, ADU | Martinez · Contra Costa County | — | — |
| Joe's Reliable Remodeling | Joe's Reliable Remodeling | — | (925) 798 3300 | GC, remodel, ADU | Pacheco · Contra Costa County | — | — |
| Joel Banducci Landscape | Joel Banducci Landscape | — | (510) 910 1915 | Windows, patio, painters | El Sobrante · Contra Costa County | — | — |
| Joel Hewatt Company INC | Joel Thomas Hewatt | — | (925) 252 0200 | GC, remodel, ADU | Pittsburg · Contra Costa County | — | — |
| Joes Professional Plumbing | Joes Professional Plumbing | — | (925) 831 9339 | Other | Danville · Contra Costa County | — | — |
| Joey Mota Landscaping INC | Joey Lee Mota | motalandscaping@att.net | (510) 816 5149 | Windows, patio, painters | Danville · Contra Costa County | — | — |
| Johanson Construction | Fredric Harold Johanson | — | (925) 947 0158 | GC, remodel, ADU | Alamo · Contra Costa County | — | — |
| John 316 Construction INC | Sergio Enrique Bustos | — | (925) 759 9002 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| John A Marzo Jr Construction | John Anthony Jr Marzo | — | (925) 674 1339 | Electricians | Pleasant Hill · Contra Costa County | — | — |
| John A Russo | John A Russo | — | (415) 922 1200 | GC, remodel, ADU | Danville · Contra Costa County | — | — |
| John Arthur Welding INC | Jeffrey Mccune | — | (925) 577 8893 | Other | Antioch · Contra Costa County | — | — |
| John Bogert | John Bogert | — | (925) 687 2265 | Windows, patio, painters | Concord · Contra Costa County | — | — |
| John D Hartvickson | John D Hartvickson | — | (925) 687 1777 | HVAC | Concord · Contra Costa County | — | — |