Emergency services were deployed at around 6.55 pm on Thursday after a call from the owner of a neighbouring flat who had heard a smoke alarm sounding and the smell of smoke.
Four firefighters wearing breathing apparatus entered the smoke-filled property and rescued the two men shortly after their arrival.
A male in his mid-60s was seen being aided by firefighters, while another 2 firefighters carried a male believed to be in his mid-50s out of the property.
Both were treated at the scene by paramedics and taken to hospital for treatment at the Queen Alexandra in Cosham
Crews after rescuing the men used a hose reel jet and positive pressure ventilation to put out the blaze.