The blaze was reported near the intersection of Monterey and Blossom Hill roads at about 2:30 p.m., San Jose fire Capt. Chuck Rangel said.
Three civilians and one firefighter suffered burns. The civilians were taken to a local hospital while the firefighter was released after being treated for his injuries at the scene, Rangel said.
The fire was under control at 3:40 p.m., he said.
The mobile home has been deemed uninhabitable, according to Rangel. He said the cause of the fire remains under investigation.