The two-alarm fire was reported at about 10:30 p.m. at a home in the 200 block of Arbor Street, Vacaville fire Battalion Chief John Jansen said.
Firefighters arrived to find heavy flames coming from the front window and front door of the home. The fire spread into nearby trees and was threatening a neighbor's home, Jansen said.
After extinguishing the blaze in the front part of the home, firefighters searched the home where they found the deceased man, he said.
The fire was controlled about 25 minutes after it was reported, according to Jansen. No one else was injured, and no neighboring homes were damaged.
Fire investigators are at the home today to try to determine the cause of the fire. It is believed to have started accidentally, possibly due to a candle or an electrical problem, Jansen said.
The Police Department is also involved in the investigation, as is standard procedure when there is a fatality in a fire, he said.