| O.c.o. Landscaping | O.c.o. Landscaping | — | (707) 439 5481 | Windows, patio, painters | Petaluma · Sonoma County | — | — |
| O2 Treehouse Commercial INC DBA 02 Treehouse Construction | Dustin David Feider | — | (323) 404 8014 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Oak 3 Painting | Oak 3 Painting | — | (707) 239 3961 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| Oak And Stone Landscape | Mendieta Omar Salinas | kperkins@oakstonelandscape.com | (415) 250 7536 | Windows, patio, painters | Petaluma · Sonoma County | — | — |
| Oak River Landscaping INC | Medina Martin Martinez | officemanager@oakriverlandscaping.com | (415) 571 4199 | Windows, patio, painters | Petaluma · Sonoma County | — | — |
| Oak Shadows Construction Company Incorporated | Michael Donald Flowers | — | (707) 433 9324 | GC, remodel, ADU | Healdsburg · Sonoma County | — | — |
| Oak Street Refrigeration INC | Stephen Arthur Garcia | — | (707) 996 0417 | HVAC | Sonoma · Sonoma County | — | — |
| Oakmont's Painting Services | Ochoa Barragan Rafael | — | (707) 528 8222 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| Oakwood Construction INC | Richard Wayne Eichenholz | — | (707) 874 1155 | GC, remodel, ADU | Occidental · Sonoma County | — | — |
| Oasis Heating & Cooling | Oasis Heating & Cooling | eduardk2007@yahoo.com | (707) 696 4791 | HVAC | Santa Rosa · Sonoma County | — | — |
| Oasis Pump & Drilling | Anthony Joseph Adiego | — | (707) 762 4028 | HVAC | Petaluma · Sonoma County | — | — |
| Oc Maciel Construction | Omar Cordero Maciel | amkryukov@gmail.com | (707) 320 3722 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Oc Painting Pros | Jose Armando Orozco Meza | armando.ocpaintingpros@gmail.com | (707) 843 8387 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| Ocal Construction & Remodeling INC | Omar Cristian Arriaran | — | (707) 696 7051 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Occidental Plumbing | Occidental Plumbing | — | (707) 508 5378 | Other | Occidental · Sonoma County | — | — |
| Ochoa Plumbing | Ochoa Plumbing | info@ochoaplumbing.com | (707) 732 3735 | Other | Rohnert Park · Sonoma County | — | — |
| Ocl Landscaping LLC | Osiel Alejandro Jr Gutierrez | — | (707) 385 9803 | Windows, patio, painters | Rohnert Park · Sonoma County | — | — |
| Odyssey Home Inspection Inc. | Odyssey Home Inspection Inc. | tyler@odysseyhomeinspection.com | (916) 906-3770 | Inspectors | Santa Rosa · Sonoma County | — | — |
| Ogden Decor & Design | Ogden Decor & Design | — | (415) 497 3433 | Windows, patio, painters | Petaluma · Sonoma County | — | — |
| Ohana Construction INC | Kimo Thomas Garrigan | — | (707) 782 0850 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| Ohmic Electric | Oliver Patrick Streb | %20oliverstreb@ohmicelectric.com | (415) 902 1431 | Electricians | Cloverdale · Sonoma County | — | — |
| Old Caz Construction INC | Mickey Newton Grider | oldcazconstruction@gmail.com | (707) 479 8257 | GC, remodel, ADU | Cazadero · Sonoma County | — | — |
| Old Dog Water Treatment LLC | Silas Ben Maizner | — | (707) 949 2483 | Other | Cotati · Sonoma County | — | — |
| Old Redwood Heating And Cooling | Old Redwood Heating And Cooling | — | (707) 548 8445 | HVAC | Windsor · Sonoma County | — | — |
| Old West Landscaping | Jacob Kelly Lippincott | — | (707) 710 0075 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| Old World Construction And Development | Dominic Antonio Cerniglio | — | (310) 628 9008 | GC, remodel, ADU | Sebastopol · Sonoma County | — | — |
| Olderbak Tile Incorporated | Daniel Wayne Olderbak | — | (707) 795 1187 | Other | Cotati · Sonoma County | — | — |
| Oleascape LLC | Frederic Michel Autran | — | (415) 595 0815 | Windows, patio, painters | Cloverdale · Sonoma County | — | — |
| Oleksandr Ponomarov | Oleksandr Ponomarov | — | (707) 889 1052 | GC, remodel, ADU | Occidental · Sonoma County | — | — |
| Oliver Construction | Cory Douglas Oliver | — | (707) 217 0099 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Oliver Designs Painting | Oliver Designs Painting | — | (707) 535 0203 | Windows, patio, painters | Fulton · Sonoma County | — | — |
| Olivera's Plumbing | Olivera's Plumbing | oliverasplumbing@gmail.com | (707) 318 2438 | Other | Santa Rosa · Sonoma County | — | — |
| Olvera Construction | Jeffrey John Olvera | — | (707) 327 8142 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| Olympus Painting | Olympus Painting | olympuspainting73@gmail.com | (707) 490 4765 | Windows, patio, painters | Windsor · Sonoma County | — | — |
| Omar Painting | Omar Painting | — | (707) 480 9908 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| Omar's Flooring | Omar's Flooring | — | (707) 774 2146 | Other | Petaluma · Sonoma County | — | — |
| On A Limb Tree Service LLC | Demetri Larue Voelker | — | (707) 494 5255 | Other | Bodega · Sonoma County | — | — |
| On Fire | Eleanor Mc Mullen Butchart | contacto@on-fire.com | (707) 526 3322 | Other | Santa Rosa · Sonoma County | — | — |
| On Grade General Engineering INC | David Allen Greger | — | (707) 843 7702 | Other | Santa Rosa · Sonoma County | — | — |
| On The Grind Stumps | On The Grind Stumps | — | (707) 640 5319 | Other | Santa Rosa · Sonoma County | — | — |