The fire was reported shortly before 6:30 p.m. at a single-family home at Moeser Lane and King Drive, El Cerrito fire Battalion Chief Michael Bond said.
A man was at home with his mother and his 11-year-old granddaughter when the fire broke out, Bond said.
He tried to get his mother out of the house but she died in the fire.
The man was taken to a hospital afterward, and the girl was not hurt, Bond said.
Firefighters had the two-alarm blaze under control shortly after 7 p.m., but the fire caused an estimated $700,000 in damage and Bond said it was "pretty much a total loss of the house."
The residents have found temporary housing with nearby family members, Bond said.
The cause of the fire is under investigation, although Bond said it appears to have been accidental and may have involved candles.