The infant was playing in a bouncer when she was approached by the fox and bitten.
The family immediately called emergency services who rushed to the scene and treated the child.
After being taken to hospital the baby was given a tetanus injection and received antibiotics.
The fox is believed to have been frequently visiting the garden in the days before the horrifying attack.
A family member has now shared a photo of the fox online in a bid to warn other people in the area.
A South Western Ambulance Service spokeswoman said: “We were called on Tuesday at 1.47pm to an incident in the West Park area of Plymouth involving a suspected animal bite.
“We attended with a rapid response vehicle.
“A female patient was treated at the scene for minor injuries.”
Fox attacks are rare but cases in which babies are specifically targeted do exist.
In 2013 a fox attacked a four-week-old baby in south London. The boy was taken to hospital and police launched an inquiry.
Then-Mayor of London Boris Johnson said more needed to be done – even if such incidents were uncommon.
He said: “This sort of attack, though terrible, is rare – but we must do more to tackle the growing problem of urban foxes.
“They may appear cuddly and romantic but foxes are also a pest and a menace, particularly in our cities.
“This must serve as a wake up call to London’s borough leaders, who are responsible for pest control.
“They must come together, study the data, try to understand why this is becoming such a problem and act quickly to sort it out.”
An RSPCA spokeswoman said it was unusual for foxes to attack people.
She said: “It’s not typical fox behaviour at all.
“Foxes will come closer to a house if there are food sources.
“Then they can become quite bold, but they usually do back off and run away when there’s people around.”