The fire broke out at a residence in the 44700 block of Foxton Avenue at about 11:30 p.m., according to the Los Angeles County Sheriff's Department.
More than two dozen L.A. County firefighters were able to knock down the flames in about 30 minutes, but there was extensive damage to the home. It was not immediately known if any one was injured.
"The house is not livable," L.A. County Fire Department Capt. Scott Polgar told KTLA-TV.
About 15 to 20 cats and kittens lived at the home, firefighters said. It was not immediately clear how many died, but others -- including three 8-week old kittens -- made it.
"The firefighters did a heroic effort in saving those cats," said Polgar.
A woman who appeared either be a resident or caretaker of the pets could be seen helping to administer oxygen to one of the rescued cats.
"She was actually giving one of the cats mouth-to-mouth, from what I remember at the scene," Polgar said. "I'm not sure if that cat has survived or not, but she was trying to do her best to save the cat."
No injuries were reported. The cause of the blaze was under investigation.