Authorities say Alexis Urbina died of his injuries Thursday at a hospital.
Phoenix police say the teen was found unconscious and covered in blood in the family's living room about 1:30 p.m. Tuesday.
They say there was no obvious sign of forced entry into the house, but Urbina's family says some of his boxing memorabilia is missing.
Police say it's unclear if robbery is a motive and they're waiting for an autopsy to determine the cause of death.
Urbina won the 141-pound Youth Men's Division at the USA Boxing National Championships in April at Spokane, Wash.