The accident occurred along the Narayangadh-Mugling highway in Chitwan district, 160 km south of Kathmandu, this morning.
The passenger bus heading towards Kathmandu from Narayangadh collided with a truck heading towards Mugling from Narayangadh, police said.
The injured passengers were admitted to the College of Medical Sciences, Chitwan, for treatment.
Speeding was said to be the cause of the accident.