The blaze was reported at 2:05 a.m. after a man smelled smoke at a residential structure in the 300 block of Ashland Avenue, according to the Santa Monica Fire Department.
Firefighters responded to the scene, where intense flames burned through two floors and multiple rooms. The fire was extinguished about 35 minutes after it was first reported.
Investigators determined it began in a third-floor patio area at the location. No one was injured.
The cause of the incident is under investigation.