The tenant described the 150-pound reptile as "gentle as a puppy" after animal control workers were called to the Kansas City home on Wednesday. The workers also found two boa constrictors and a rabbit.
The Kansas City Star reports a specialist removed the alligator, which was at least 6 feet long. No one was injured.
The tenant, Sean Casey, said he'd owned the alligator for four years and named it Katfish. He called the reptile "a big cuddly lizard."
A spokesman for the city's Neighborhood and Housing Services Department says Kansas City doesn't allow homeowners to have alligators.
Katfish will be temporarily housed at the Monkey Island Rescue and Sanctuary in nearby Greenwood. The snakes and rabbit were taken to an animal shelter.