The unidentified girl was struck in the head Friday by a bullet while she was out on the street with adults and other children in the town Oberaurach, north of Nuremberg.
While fireworks are commonly used in Germany during New Year's celebrations, live bullets aren't usually fired.
A spokeswoman for police in the Lower Franconia region says the bullet was fired from a small-caliber firearm that would have required a permit.
Police are appealing for information to help find the weapon and identify the shooter.