Up to five gunmen tried to storm the building, in the city of Peshawar.
Exchanges of fire were heard in the area, as police attempted to repel the attack. Unconfirmed reports say three attackers were killed.
Peshawar lies near the lawless tribal belt – a stronghold of Taliban and al-Qaeda militants.
The gunmen – armed with assault rifles and bombs – attacked the police station in the heart of the city on Friday morning.
Some reports say they blew themselves up during the assault.
No group has so far claimed responsibility for the attack.
Peshawar has recently been the target of several recent attacks.
On Thursday, at least 12 people were killed and 30 injured after a car bomb hit a bus stop in the city.
Militants often carry out attacks across the north-west in retaliation for operations by the army against them in Pakistan’s tribal areas.