The accident took place late Thursday night near Kohat Tunnel on Indus Highway, Xinhua news agency reported citing the police as saying.
Rescue teams had to cut through the passenger coach to retrieve the bodies and the injured trapped inside the vehicle, the police said.
Authorities said the accident occured due to the over-speeding of the trailer.
The passenger coach was travelling from the northwest Lakki Marwat district to Peshawar, the provincial capital.
Following the accident, rescue teams and police reached the scene and shifted the injured people to a nearby hospital.