The girl died on the spot, police said.
The incident took place at Vighnaharta building in MHADA complex, Byculla, central Mumbai, at around 12.30 pm.
According to the police, the victim's mother, who is a traffic constable and lives on the 15th storey of the building, had a quarrel with another woman, her neighbour, this morning.
Some time later the other woman allegedly threw the policewoman's five years old daughter down from the building's common balcony.
Police said a case was being registered and no arrest had been made yet.