| Coastal Creations Construction | Tye James Davis | — | (707) 799 9707 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Coastal Landscape | Coastal Landscape | — | (707) 799 7019 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| Coastal View Builder | Coastal View Builder | — | (707) 387 7758 | GC, remodel, ADU | Sebastopol · Sonoma County | — | — |
| Coastside Concrete & Construction INC | Mark Edmund Sousa | — | (707) 695 6022 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Coating Painting Waterproofing INC | Jose Vega Villagomez | — | (707) 217 1985 | Windows, patio, painters | Windsor · Sonoma County | — | — |
| Codding Construction Co | Linda Marie Morgan | — | (707) 978 5807 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Codding Maintenance | Linda Marie Morgan | — | (707) 978 5800 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Coggins Electric | Sean Liam Coggins | — | (530) 545 1943 | Electricians | Santa Rosa · Sonoma County | — | — |
| Coggins Fence & Supply INC | Jim Walter Bennett | — | (707) 546 0284 | Other | Santa Rosa · Sonoma County | — | — |
| Cogliandro Construction North INC | Kevin Peter Cogliandro | — | (707) 874 6165 | Other | Camp Meeker · Sonoma County | — | — |
| Cohan Structures | Olin Kenneth Cohan | — | (707) 889 6468 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Cold Air Performance & Heating INC | Dustin Alexander Woolf | — | (707) 708 2400 | HVAC | Santa Rosa · Sonoma County | — | — |
| Coldflo Mechanical INC | Kenneth Scott Ragan | office@coldflo.com | (707) 234 4744 | HVAC | Healdsburg · Sonoma County | — | — |
| Cole Construction | Matthew Gerard Cole | — | (707) 478 7763 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Cole Crew Construction | Adam Jeffrey Cole | — | (415) 832 9962 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Coleman Construction | Ricky Lee Coleman | — | (707) 756 0447 | GC, remodel, ADU | Windsor · Sonoma County | — | — |
| Coleman Construction | Wendell Jr Coleman | — | (707) 363 7067 | GC, remodel, ADU | Boyes Hot Springs · Sonoma County | — | — |
| Coleman Custom Construction | Benjamin Andrew Coleman | bencolemancustom@yahoo.com | (707) 328 5260 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Colibri Construction | Rafael Miguel Cervantes Calderon | luke@colibriconstruction.com | (707) 775 7947 | GC, remodel, ADU | Sonoma · Sonoma County | — | — |
| Colin Desmond Doyle | Colin Desmond Doyle | — | (707) 823 5020 | GC, remodel, ADU | Sebastopol · Sonoma County | — | — |
| Collard Electric | Michael David Collard | — | (707) 526 4084 | Electricians | Santa Rosa · Sonoma County | — | — |
| Collins Electric | Brett Christopher Collins | — | (707) 280 0805 | Electricians | Windsor · Sonoma County | — | — |
| Color Essentials Painting Co | Jose Carlos Garcia Tafolla | contact@coloressentialspainting.com | (707) 228 7444 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| Color Flow Painting | Color Flow Painting | — | (415) 516 0047 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| Colorful Impression Landscapes INC | Ana Maria Avalos | — | (707) 396 6378 | Windows, patio, painters | Windsor · Sonoma County | — | — |
| Colton Edson Construction INC | Colton Rae Edson | coltonedson@gmail.com | (707) 326 3093 | GC, remodel, ADU | Sebastopol · Sonoma County | — | — |
| Combs Electric | Richard E Combs | — | (707) 578 1814 | Electricians | Santa Rosa · Sonoma County | — | — |
| Comeaux Construction | David James Comeaux | — | (707) 540 1221 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Comet Construction INC | Thaddeus Alfonso Mazzoni | — | (707) 495 0413 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Comfort Connection Heating & Air Conditioning | Erik Joseph Botello | — | (707) 495 7403 | HVAC | Rohnert Park · Sonoma County | — | — |
| Comfort Factor Mechanical INC | Eric James Hall | — | (707) 495 2861 | HVAC | Sebastopol · Sonoma County | — | — |
| Commercial Decor Group INC | Trae' Michael Seely | info@commercialdecorgroup.com | (707) 484 7352 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Commercial Kitchen And Appliance Service | Rick Lea Dabney | — | (707) 477 1019 | HVAC | Santa Rosa · Sonoma County | — | — |
| Communications Express | Montie Karr Fortkamp | — | (707) 579 1300 | Other | Santa Rosa · Sonoma County | — | — |
| Community First Construction Corp | Jose Luis Gama | — | (415) 375 1237 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Community Soil INC | Paul Joseph Tantarelli | — | (707) 889 1744 | Windows, patio, painters | Windsor · Sonoma County | — | — |
| Complete Concrete Construction | Sione Maloni Hausia | — | (510) 274 3875 | Other | Rohnert Park · Sonoma County | — | — |
| Complete Construction Group | Luke Gregory Young | — | (707) 293 8707 | Electricians | Sebastopol · Sonoma County | — | — |
| Complete Masonry Services | Jeff Landon Gentry | — | (707) 542 0477 | Other | Santa Rosa · Sonoma County | — | — |
| Compton Fabrication | Gregory Neal Compton | — | (707) 829 1663 | Other | Sebastopol · Sonoma County | — | — |