The accident happened around 11:41 a.m. in the 2200 block of Cottman Avenue, near Horrocks Street.
Police say the 35-year-old man and the 4-year-old boy ran into traffic for an unknown reason.
The SUV that hit the pair had a green light at the time of the crash, police say.
The child was taken to St. Christopher's Hospital for Children in serious condition with head injuries. The father was taken to Albert Einstein Medical Center in stable condition.
The identities of the victims were not yet released.
The driver of the striking vehicle stopped at the scene.
An investigation into exactly what happened continues.