A 7ft (2.1m) boa constrictor fell from an attic onto the landing as the hatch was opened.
Stephen Hope and his wife Annette were left “stunned” after the reptile fell at their home in Stockingford, Nuneaton.
“I’d only gone up there to look for some books, it was pretty frightening”, Mr Hope said.
The snake, thought to be 14 years old, is now being cared for at the Nuneaton and Warwickshire Wildlife Sanctuary.
Warwickshire Police said the force was called to reports of a snake at a property at 19:15 BST on Friday.
The snake, now nicknamed Lofty, is “doing well” according to the wildlife sanctuary’s owner Geoff Grewcock.
Mr Grewcock said: “No-one’s got any idea how it got in the attic.
“Maybe someone’s just dumped it and it crept in there”.
Mr Hope said they would be getting a builder to check out the attic, “just to make sure there’s no other snakes up there”.