The blaze, which started as a result of a faulty fish tank, suddenly ignited resulting in the couple dashing for safety before fire crews came to the rescue in Sultan Road, Buckland, at 1.45am.
Firefighters from Southsea battled to put out the ‘large flames’ which had caused a window to be smashed in the first floor bedroom.
Four breathing apparatus and a command support unit from Portchester were needed to combat the blaze.
The two occupants of the property, both thought to be in their 50s, were treated for smoke inhalation by paramedics.
Crew manager Christopher Norgate said: ‘The fire was caused by a faulty fish tank which had ignited causing a fire in the first floor bedroom. Both the occupants were out of the property by the time we attended and needed first aid treatment.’
The fire was extinguished within an hour.