A till and float were also stolen during the incident, which happened at VetSavers on Newcastle Avenue on the night of Friday, May 13.
VetSavers staff are now warning shops in the area to keep both their donation boxes and tills secure- and are demanding the thief return money raised by them and their clients.
Head nurse Suzhy Winfield, who discovered the theft when she came to open the surgery at around 8.30am the next day, said: “The till can be replaced, but we work hard to raise money for the Blue Cross and seeing that it had been stolen was just soul-destroying.
“It was a mindless theft but we are hoping the thief might find it in their heart to return what they have taken.”
The charity box was thought to have contained around £30. This would have been added to extra funds raised by staff through raffles and other fundraisers for the Blue Cross, a charity which helps animals in need.
Anyone who knows anything about this incident or saw anything suspicious should call Nottinghamshire Police on 101 quoting incident number 142 of May 13.