The attack happened near Val Vista and Germann Roads Sunday afternoon.
Gilbert police Sgt. Jesse Sanger said the babysitter was watching five children at her home while their parents were out of town. The children ranged in age from 2 1/2 to 9 years old.
Sanger said three of the babysitter's dogs got into a fight and she tried to break it up. The toddler somehow got involved in the fray and was injured. Officials said the boy was taken to Gilbert Mercy Hospital where he later died.
The babysitter was taken to a local hospital to be treated for her injuries.
Animal Care and Control spokeswoman Melissa Gable said after the attack, the babysitter realized the severity of the situation and agreed to relinquish ownership of the dogs and have them euthanized.
Gable said three of the four dogs were euthanized Tuesday afternoon.
The dogs' remains are being sent to the state lab to be tested for rabies. Gable said officials expect to have the test results by the end of the week.
The one dog that was not euthanized will be returned to its owner. The dog was the mother of the three other dogs, and according to the owner, was not involved in the attack.
Animal Care and Control spayed the dog. Officials say it is unable to have any more puppies.