Units responded to reports of fire at a home at 162 Bendorf Drive in southeast San Jose at around 12:15 a.m., fire Capt. Scott Kouns said.
Arriving firefighters found one unit of a duplex fully engulfed in flames, Kouns said.
Three residents were apparently inside the unit when the fire began. One resident was unaccounted for until firefighters located that person in the home's backyard, Kouns said.
The victim was taken to a hospital to be treated for minor injuries.
No other injuries have been reported.
Both units were damaged in the fire, Kouns said, and six residents have been displaced.
The blaze was controlled by 2 a.m.
The cause is under investigation.