The rodent was in his cage at around 2am yesterday when an electric fire caused a blaze at a terraced house in Torquay, Devon.
Luckily the cage door was unfastened, but not for Fido the easy option of deserting the family sleeping upstairs and saving his own skin.
Instead, he managed to jump out of his cage, scurry out of the blazing room, climb up 15 stairs and scratch at the bedroom door.
Single mum Lisa Gumbley, 29, was fast asleep inside with daughters Megan, nine, and Shannon, three. Megan said: "The noise of his scratching woke me up and I got up to go to the toilet."
Lisa said: "If it wasn't for Fido we'd all be dead now. They say that rats desert sinking ships but our Fido's a real hero. He didn't run off but came upstairs to save us. We all love him to bits."
The family managed to get out the house and call the fire brigade, which quickly got the blaze under control.
But the family's 10-month old Alsatian Naseem is in the doghouse after failing to wake the family.
A spokesman for Devon Fire Brigade said: "We've heard of pet dogs and pet cats waking their owners. Even a parrot. But never a rat."