Animal rescue officer Sian Robertson said they were alerted when a nurse became suspicious while feeding it.
She said: "When I arrived, I took one look at the little fluffy animal and knew she was a fox cub - and a very cute one at that!"
The Scottish SPCA is caring for the animal, now named Husky, and it will be released into the wild in the summer.
Ms Roberston said they were contacted by Julie Innes Veterinary Surgery on Friday, after a nurse became doubtful it was a puppy.
She said: "The nurse had already wrapped her up so I took her up to our wildlife centre where she will be hand-reared with minimal human contact.
"Husky will then be introduced to other fox cubs and will be released during summer in a carefully selected site with the land owners permission."

The blaze at Wythenshawe Hall, which broke out at about 03:30 GMT, destroyed the roof and caused extensive damage to an upper floor.
Insp Luke Breakspear, of Greater Manchester Police, said the fire investigation was in its infancy.
More than 50 firefighters tackled the fire at the timber-framed Tudor hall, which was built in 1540.
Wythenshawe was home to the Tatton family for about 400 years. It was donated to local people in 1926 and was previously run as a museum and art gallery.
Peter Lamb, Incident Commander with Greater Manchester Fire and Rescue Service, said having a sprinkler system would have made a difference to quenching the fire.
"We recommend sprinklers in all buildings where possible - it did have an automatic fire alarm system and thankfully that gave us the early warning which got us here within minutes, whereas if it hadn't had that would have been in serious trouble," he said.
Paul Selby, vice-chair of the Friends of Wythenshawe Hall, said: "As a result of the amazing work of Greater Manchester Fire and Rescue Service the hall is safe - obviously it will need a new roof and some cosmetic work inside."
Source: Friends of Wythenshawe Hall

Sea Watch said men from the speedboat boarded the dinghy and beat migrants with sticks, causing a "mass panic".
At least four of the 150 people on board the dinghy fell into the water and drowned, Sea Watch said.
A spokesman for Libya's naval forces in Tripoli said he had not heard about the incident.
The motive for the attack was not clear, but Ruben Neugebauer, a spokesman for Sea Watch, said the attackers were attempting to steal the dinghy's engine.
Mr Neugebauer said that 25 people remained missing.
Sea Watch, a German organisation, said in a statement: "The violent intervention of the Libyan Coast Guard caused a situation of mass panic on board the rubber boat in distress.
"One tube of the rubber boat collapsed, causing the majority of the 150 people to slip into the water."
About 120 people were rescued and brought aboard the Sea Watch 2 ship. Four were unconscious and receiving treatment.
Italy's coast guard confirmed that Sea Watch had been involved in some of the nine rescue operations taking place on Friday.
Both the Libyan and Italian coast guards said they had received no information about the attack yet.
Italy has taken in more than 146,000 boat migrants so far this year and is on track to see more arrivals than last year, when 153,000 arrived.
In August, the Doctors Without Borders humanitarian group, which operates rescue ships off the coast of Libya, said it was attacked by armed men on a Libyan navy boat.
The Libyan navy said it thought the vessel was involved in people smuggling.
A week-old fox cub was mistaken for an abandoned puppy after it was found by a road and handed in to a vet surgery.
[NEXT_CONCEPT]
A fire that badly damaged a 16th Century hall in Manchester is "suspicious", police have said.
[NEXT_CONCEPT]
At least four migrants have died after a speedboat labelled "Libyan Coast Guard" attacked a dinghy, according to a migrant rescue organisation.