| City Bay Electric Incorporated | Luis Otoniel Vela Pineda | — | (925) 594 0313 | Electricians | Walnut Creek · Contra Costa County | — | — |
| City Electric Service INC | Michael Joseph Mendez | — | (510) 527 5373 | Electricians | Crockett · Contra Costa County | — | — |
| City Fire Protection | City Fire Protection | info@cityfireprotection.co.uk | (650) 515 5044 | Other | San Pablo · Contra Costa County | — | — |
| City Green Builders | City Green Builders | — | (925) 222 8581 | GC, remodel, ADU | Pacheco · Contra Costa County | — | — |
| City Mechanical INC | Ronald Alan Tinkey | service@citymechanical.com | (510) 724 9088 | HVAC | Hercules · Contra Costa County | — | — |
| Cjm Development | Cjm Development | — | (925) 360 3502 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Ck Landscape Solutions LLC | Matthew Gary Cartwright | — | (925) 570 4463 | Windows, patio, painters | Danville · Contra Costa County | — | — |
| Claiborne Construction | Gerold Lee Claiborne | — | (916) 380 8777 | GC, remodel, ADU | Clayton · Contra Costa County | — | — |
| Clancy's Precision Painting | Clancy's Precision Painting | — | (925) 212 2501 | Windows, patio, painters | Martinez · Contra Costa County | — | — |
| Claremont Construction INC | Ian Samuel Stonerock | — | (925) 332 7281 | GC, remodel, ADU | Pleasant Hill · Contra Costa County | — | — |
| Clarke Construction | David Cornell Clarke | — | (925) 586 1855 | GC, remodel, ADU | Pleasant Hill · Contra Costa County | — | — |
| Class A Drain & Plumbing INC | Edilsar Abdias Cordero Marroquin | — | (415) 342 6382 | Other | Richmond · Contra Costa County | — | — |
| Classic Heating And Air Conditioning | Classic Heating And Air Conditioning | — | (925) 293 6541 | HVAC | Concord · Contra Costa County | — | — |
| Classy Glass Tinting | Classy Glass Tinting | cgt@comcast.net | (925) 754 8468 | Other | Antioch · Contra Costa County | — | — |
| Claudio Luiz Volpe Rohrsetzer | Claudio Luiz Volpe Rohrsetzer | — | (510) 331 5640 | Windows, patio, painters | El Cerrito · Contra Costa County | — | — |
| Claw Communications | Mark Alan Holtzclaw | — | (925) 382 8005 | Other | Pinole · Contra Costa County | — | — |
| Clayton Brothers Heating And Air INC | Nathaniel Monroe Huffine | — | (925) 331 8388 | HVAC | Clayton · Contra Costa County | — | — |
| Clayton Home Inspection Services | Clayton Home Inspection Services | — | (925) 672-9405 | Inspectors | Clayton · Contra Costa County | — | — |
| Clayton Roofing Replacement & Repair | Clayton Roofing Replacement & Repair | — | (833) 244-3033 | Other roofers | Clayton · Contra Costa County | — | — |
| Clayton Valley Mechanical Heating And Air Conditioning | Walter Harvey Ii Moore | — | (925) 672 0930 | HVAC | Clayton · Contra Costa County | — | — |
| Clayton Valley Painting | Wayne Joseph Buckman | — | (925) 260 4143 | Windows, patio, painters | Brentwood · Contra Costa County | — | — |
| Clean Air HVAC INC | Roy Dean Branda | — | (925) 270 6607 | HVAC | Concord · Contra Costa County | — | — |
| Clean Lakes INC | Thomas John Mc Nabb | — | (925) 766 8862 | Other | Martinez · Contra Costa County | — | — |
| Clean N Seal INC | Rachel Lynn Pritchett | — | (925) 418 4221 | Windows, patio, painters | Brentwood · Contra Costa County | — | — |
| Clear Contracting INC | Mejia Janet | — | (925) 206 0391 | GC, remodel, ADU | Oakley · Contra Costa County | — | — |
| Clear Day Energy | Joshua Lee Aldrich | — | (925) 350 4121 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| Clear Dry Ice Solutions | Clear Dry Ice Solutions | info@indiantypefoundry.com | (916) 926 1554 | Other | Concord · Contra Costa County | — | — |
| Clear Plumbing | Clear Plumbing | — | (510) 778 8800 | Other | Richmond · Contra Costa County | — | — |
| Clear Structure Concrete | Jesse Matthew Galletti | — | (925) 382 7095 | Other | Martinez · Contra Costa County | — | — |
| Clear View Glass Company | Troy Ryan Connor | — | (925) 202 8195 | Windows, patio, painters | Discovery Bay · Contra Costa County | — | — |
| Clear View Roofing | Kumar Rajnesh | — | (925) 305 9892 | Other roofers | Walnut Creek · Contra Costa County | — | — |
| Clear Water Mechanical Plumbing & Underground | Guerra Selso | — | (925) 679 3100 | HVAC | Clyde · Contra Costa County | — | — |
| Clearly Different INC | Lori Janell Duran | — | (925) 743 0417 | Pool | Danville · Contra Costa County | — | — |
| Clearstream Communications INC | Daniel Anthony Scholl | — | (650) 271 2040 | Other | Pittsburg · Contra Costa County | — | — |
| Cliff Swisher Custom Concrete INC | Clifford Fred Swisher | — | (925) 946 0956 | Other | Walnut Creek · Contra Costa County | — | — |
| Clifford N Beck | Clifford N Beck | — | (925) 890 9431 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Clint Shaw General Contractor | Clint Shaw General Contractor | — | (925) 788 1350 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Closets And Beyond INC | Barket Shrabi | — | (925) 822 4048 | Other | Brentwood · Contra Costa County | — | — |
| Cloud Electric | Dwayne Dean Cloud | — | (925) 565 0822 | Electricians | Antioch · Contra Costa County | — | — |
| Cloverwood Construction INC | Justin Patrick Azarias | — | (925) 542 6723 | GC, remodel, ADU | Concord · Contra Costa County | — | — |