The woman, her dog and seven cats survived, NBC News reported Wednesday.
Officials said the fire broke out about 1:45 a.m. Tuesday in the home of Carole Miller, founder of the Stanford Cat Network. The cats were sleeping in crates at the time of the fire, preventing their escape.
Investigators said Miller was sleeping on the couch when the fire started in a bedroom. Cause of the blaze has not been determined.
Miller, in her 70s, began the cat rescue group in 1989 to save homeless cats at Stanford University where she was a research administrator, the San Jose Mercury News reported.
The cats "were like my children," Miller said, adding they were "well cared for and terribly loved."
Miller said she planned to take the dead cats to Napa, where they would be cremated. The surviving cats are in the custody of the San Jose animal services department.