The boa constrictor, said to be almost two metres long, was caught slithering across the kitchen blind of the fifth-floor apartment in the Rifredi area of Florence on Friday morning, La Nazione reported.
The couple awoke at around 5am after hearing noises coming from the kitchen and initially thought it was a burglar, the newspaper said.
Police, firemen and staff from the State Forestry Corps (Corpo forestale dello Stato) were called to the scene and the snake was taken to an animal sanctuary in nearby Prato.
Police are now trying to ascertain how the snake entered the apartment and who its owner is. The reptile was most likely kept illegally, according to a report on the website, Italia Globale.
The boa constrictor is a non-poisonous snake which is found in the wilds of north, central and South America, as well as some islands in the Caribbean.
The snake is dangerous if attacked, and will bite another animal or person. The venom is not dangerous but can be very painful.
Several boa constrictors have been found on the loose in Europe, including one that was caught on a train in France in January 2012.
In the UK last summer one went on the loose in the coastal city of Portsmouth after a man through it into a hedge when a taxi driver refused to allow it in his car.