| Comstock Builders | Comstock Builders | — | (707) 481 9325 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Comstock Construction | Ryan Kelii Comstock | — | (707) 695 1794 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Con Mara Gardens INC | Miguel Avina Chavez | miguel@conmaragardens.com | (707) 938 1061 | GC, remodel, ADU | Sonoma · Sonoma County | — | — |
| Concept Design Develop INC | Brian Michael Byrne | — | (707) 228 7465 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Concepts Conceived INC DBA Kaelin Construction | Colin Geoffrey Scott | — | (808) 896 5819 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Condor Construction | Matthew Aaron Condie | — | (707) 595 0038 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Conley Plumbing | Dale Cary Conley | — | (707) 433 4740 | Other | Healdsburg · Sonoma County | — | — |
| Connell Construction | Connell Adam | — | (707) 328 7982 | GC, remodel, ADU | Bodega Bay · Sonoma County | — | — |
| Conner Construction | Mark Dayton Conner | — | (707) 778 6865 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Conner Consulting & Contracting | Fred Francis Conner | — | (415) 509 7056 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Conner Electric | Kenneth Lee Conner | — | (707) 953 8614 | Electricians | Petaluma · Sonoma County | — | — |
| Connolly Construction | John Edward Jr Connolly | — | (707) 888 6108 | GC, remodel, ADU | Windsor · Sonoma County | — | — |
| Conor Rounds | Conor Rounds | — | (415) 686 9923 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Conrad's Fire Protection | Ralph Conrad Gersley | — | (707) 849 5668 | Other | Santa Rosa · Sonoma County | — | — |
| Consolidated Construction Management | Michael Joseph Poirier | — | (707) 291 3898 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Constantini Heating And Air Conditioning | Constantini Heating And Air Conditioning | — | (707) 528 7168 | HVAC | Santa Rosa · Sonoma County | — | — |
| Construction Art | Randolph King Hitchcock | — | (707) 799 0824 | GC, remodel, ADU | Windsor · Sonoma County | — | — |
| Construction Solution Corp | Edward Steven Sanchez | csi@constructionsolution.com | (707) 548 5931 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Constructive Concepts Building LLC | Lucas Remington Jones | constructiveconcepts707@gmail.com | (707) 703 2893 | GC, remodel, ADU | Windsor · Sonoma County | — | — |
| Conte Construction | Raymond Matthew Conte | — | (707) 338 1787 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Contemporary Electric INC | Legorreta Armando | — | (415) 259 5591 | Electricians | Rohnert Park · Sonoma County | — | — |
| Control Systems West INC | Bruce David Borders | — | (707) 763 1108 | Electricians | Petaluma · Sonoma County | — | — |
| Conz Construction INC | Rodney Richard Robbins | — | (707) 322 7768 | GC, remodel, ADU | Healdsburg · Sonoma County | — | — |
| Cook Fire Protection | Cook Fire Protection | — | (707) 326 2811 | Other | Santa Rosa · Sonoma County | — | — |
| Cooley Construction Company INC | Robert John Jr Cooley | — | (707) 480 3614 | GC, remodel, ADU | Bodega Bay · Sonoma County | — | — |
| Coolpoint Refrigeration INC | Peter John Skalski | — | (707) 849 8540 | HVAC | Sebastopol · Sonoma County | — | — |
| Cooney Construction INC | Robert Joseph Cooney | — | (707) 658 1046 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Coonrad Construction | Warren Todd Coonrad | — | (707) 479 1017 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Coordinated Project Installations INC | Richard William Vitali | — | (707) 578 8255 | Other | Santa Rosa · Sonoma County | — | — |
| Copper Hammer Remodels INC | Denver Imo Guillory | — | (707) 486 2077 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Cordoza Concrete Services INC | Cris Andrew Cordoza | cris@cordozaconcrete.com | (707) 978 8150 | Other | Santa Rosa · Sonoma County | — | — |
| Cordoza Floors | Cordoza Floors | — | (707) 235 1902 | Other | Sebastopol · Sonoma County | — | — |
| Core Electrical Services INC | Christopher Robert Perez | — | (707) 687 5083 | Electricians | Santa Rosa · Sonoma County | — | — |
| Core Energy Systems | Core Energy Systems | — | (707) 696 4806 | Electricians | Penngrove · Sonoma County | — | — |
| Core Heating & Air Conditioning | John Salus | — | (707) 774 5003 | HVAC | Petaluma · Sonoma County | — | — |
| Core Point Plumbing INC | Marty Graham Winset | — | (707) 655 3160 | Other | Rohnert Park · Sonoma County | — | — |
| Corey Goodin Excavation | Corey Goodin Excavation | — | (415) 676 0214 | Other | Guerneville · Sonoma County | — | — |
| Corey Harms Construction | Corey Micheal Harms | corey@coreyharmsconstruction.com | (707) 326 1669 | GC, remodel, ADU | Cloverdale · Sonoma County | — | — |
| Cornelius Joy | Cornelius Joy | — | (707) 579 8847 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Cornerstone Healdsburg | Richard Wayne Plaxco | — | (707) 473 4333 | Windows, patio, painters | Healdsburg · Sonoma County | — | — |