The two-alarm blaze was reported about 5:30 a.m. at a third-level unit of The Keys condominiums, 410 N. Civic Drive, according to the Contra Costa County Fire Protection District.
The unit that burned was the only one damaged in the fire, Fire Capt. George Laing said. Residents in nearby condos were evacuated, but returned to their homes after the blaze was extinguished.
The victim's name has not been released.
The fire was contained shortly after 6 a.m. A cause has not been determined and the blaze is under investigation, Laing said.
ABC7 News contributed to this report.