Tracy Nolan tells WPXI-TV the game took her daughter across a busy highway in Tarentum during the evening rush.
She says the girl had just finished playing the game when she was hit Tuesday around 5 p.m. She remains in the hospital Wednesday with an injured collarbone and foot, as well as cuts and bruises.
The car's driver stopped and held her daughter's hand until emergency responders arrived.
The "augmented reality" game encourages players to wander in the physical world to find and catch new Pokemon on their screens.
The game's popularity has created unintended consequences in everyday life, from annoyed property owners dealing with hordes of monster hunters to store owners using the game to attract customers.