The Philadelphia coroner's office says John Bruno died Saturday at Children's Hospital of Philadelphia, where he had been under heavy sedation since the accident last Wednesday.
Police say his mother looked out a window of her Warrington home to see her son face-down and unconscious in the snow while the dog tugged at the scarf.
Police initially thought the child had collapsed from cardiac arrest while playing with the 18-month-old hound.
Police say first responders performed CPR on the boy.
A GoFundMe page set up to help the family pay medical costs says John's smile was electric and he loved "Ninja Turtles, Pokemon, superheroes and being silly."