Donna Motsinger said the former star gave her wine and a pill that left her incapacitated after picking her up at her home in a limousine in 1972. BBC reported.
Cosby, 88, has denied Motsinger's allegations, along with similar claims in a string of civil and criminal cases filed by dozens of women.
He was freed from prison in Pennsylvania in 2021 nearly three years into a sentence for sex assault after his conviction was thrown out on a technicality.
Cosby's lawyer Jennifer Bonjean told US media her client would appeal against Monday's verdict.
The jury in the Santa Monica case could award even more in punitive damages that they have yet to determine.
Motsinger, now 84, used to work as a waitress at a restaurant called the Trident in Sausalito, near San Francisco, that was a haunt for celebrities, including Cosby.
She alleged in her lawsuit that Cosby invited her to one of his stand-up comedy shows and after picking her up to drive her to the gig he gave her a pill that she thought was aspirin, according to the court papers.
"Next thing she knew, she was going in and out of consciousness," her legal action said, according to the Los Angeles Times. "The last thing Ms Motsinger recalls were flashes of light."
