Firefighters smashed through the front door of a ground floor flat in Lindon Road, Brownhills, at around 1.30am after neighbours reported seeing smoke billowing through open windows of the property.
Crews from Aldridge and Bloxwich attended the blaze and secured the property within half an hour.
The owner of the flat, which forms part of a two-storey maisonette, was not at home at the time of the blaze. No injuries have been reported.
Crew Commander Rob Evans said: "A passing taxi driver spotted smoke coming out of open windows of the property and alerted a neighbour who contacted us.
"When we arrived the front windows were open and smoke was coming out onto the street.
"The flat was unoccupied at the time and we had to force entry through the front door.
"There were two small pockets of fire in the living room and bedroom.
"We managed to put out the fires and the two rooms were left with significant smoke damage."
Mr Evans added police were on the scene investigating the suspected arson.