One-year-old Teenie was found injured by her owner Sarah Nisbett in Niddry View, Winchburgh, West Lothian, at around 4.30pm on Friday and taken to the SSPCA.
She had been shot twice in the shoulder and once in her left rear leg, which was so badly damaged that vets had "no option" but to amputate it.
Mrs Nisbett said the cat is now having to learn how to walk again.
She said: "The gun that was used must have some power because the pellet actually went through her back leg, that's why it was so badly damaged.
"She's now learning how to hop around the house, it's terrible.
"Hopefully somebody will know who's done this and let the police or SSPCA know."
The SSPCA said Teenie is "incredibly lucky" to have survived the attack.