The trailer struck the coach coming from the other side while it was travelling from Lakki Marwat to Peshawar.
There were at least 17 fatalities, including women and children. In the accident, one person suffered injuries.
Police and rescue personnel arrived at the scene quickly and moved the injured and dead to a hospital in Kohat.
Those who perished were named as Noor Rehman, Sailan, Akhtar Ali, Ashraf Ali, Adnan Khan, Irfan, Hameed, Aijaz, Sardar Ali, and driver Saifullah. Also among the dead were a wife, three children, and a lady.
After a case was registered, police began an investigation.
As a result of the disaster, many precious lives were lost, and foreign minister Bilawal Bhutto Zardari expressed his sorrow.
The foreign minister urged the relevant authorities to take action to stop similar accidents from happening again in a statement released here.