The terrified resident called the RSPCA after she saw what she thought was a dangerous reptile on two occasions.
But RSPCA workers called out to her home found it was a children's toy - and may have been a prank.
The woman had seen the snake in two different locations in the communal hallway of the flats in Fleet, Hampshire, on Thursday.
But RSPCA Inspector Jan Edwards realised the snake was just a innocent toy designed for children.
She said: "The woman spotted the snake in the communal hallway of her block of flats.
'Prank on poor woman'
"The following day she spotted it on the windowsill and contacted us to say she was worried because it didn't appear to be moving.
"I went down to help and, when I arrived, it quickly became clear that it wasn't an escaped pet snake - but a child's plastic toy.
"I think someone may have been playing a prank on the poor woman. She had been so frightened that she hadn't left her flat."
The snake has now been adopted by Jan as her van mascot.