The two-alarm blaze was reported at 510 Branham Lane E., a two-story home, at about 12:40 a.m., according to San Jose fire Capt. Barry Stallard.
The fire had been burning for "some time" when the firefighters arrived, Stallard said, and the first firefighter who went upstairs fell through the second story to the first.
He said the firefighter was not injured.
"He was fine," Stallard said. "It was like a slow-motion fall. Fortunately there was no fire beneath him because we had extinguished that."
The flames were declared under control at 2:18 a.m. and did not spread to any neighboring homes, according to Stallard.
No one was home at the time of the fire, and Stallard said the residents were visiting their son for Christmas and received notice of the blaze from their neighbors.
The cause of the fire remains under investigation, though it is not considered suspicious.