It happened about 11:30 Wednesday night inside a house on the 7500 block of Parkview Road.
Upper Darby Police Superintendent Michael Chitwood said that there was a group of people at the house with two dogs present. At one point, the dogs started attacking a woman and then an 11 month old child.
Police say the baby was bitten in the legs and buttocks.
A 16-year-old grabbed the child and ran upstairs to a bedroom.
Police arrived to the scene and put a ladder up to the side of the house and rescued the 16-year-old and the 11-month-old from the upstairs bedroom.
Officers then entered the house and a dog went to attack an officer. That officer then used a Taser on the dog.
The woman was treated for minor bite wounds and the 11-month-old is at Children's Hospital suffering from being bitten more than 20 times.
Police took away the two dogs that were in the house. There is no word yet on what caused the dogs to attack.
No charges have been filed so far in this case.