Six fire companies, three chief officers, one fire investigator and an information officer responded to 210 1/2 Los Olivos Ave. in Daly City at about 4:25 p.m. after a report of a structure fire.
Crews found a working fire in a detached rear unit behind the single-family residence. Using hose lines, firefighters extinguished the blaze.
Firefighters located the male victim inside the home during a primary search inside. The man was pronounced dead by firefighter paramedics.
The fire was contained to the rear unit, and no firefighters or other residents were injured by the fire.
The cause of the fire remains under investigation.
The San Mateo County coroner's office had not yet released the victim's name, as it was pending notification of the man's family.