Firefighters responded to a two-story home in the 1100 block of River Pine Circle at 11:51 p.m. to find thick smoke and flames coming from the garage area.
Crews had the fire contained in 15 minutes but the garage sustained significant structural damage and its contents were destroyed, fire officials said.
One resident was taken to Petaluma Valley Hospital for treatment of minor injuries.
The residents became aware of the fire when the home's smoke detectors went off. Preliminary findings indicate that the fire was accidental and may have started in an area of the garage where cigarettes are smoked, fire officials said.
The cause of the fire is still under investigation.
Parts of the home sustained moderate to heavy smoke damage, and there was water damage to the kitchen from the house's sprinkler system.
The home is uninhabitable, and the residents are staying with family members, fire officials said.
An adjacent house sustained heat damage from the fire.
The blaze was the fourth in Sonoma County within 36 hours. The other three occurred in Santa Rosa between 6 p.m. Saturday and 7 a.m. Sunday.