The motorbikes were driven by Ho Van Tuat, 14, who was carrying three friends - two boys and a girl on a motorbike and 15-year-old Ho Van Tien, who had a boy riding pillion.
Tuat, Tien and two boys riding with the former died on the spot following the collision at 00:10 a.m on a Ho Chi Minh Highway section near Ta Rut Commune in Dak Rong District.
The girl and the boy riding pillion with Tien escaped with minor injuries.
Police are investigating the accident.
In Vietnam, people must be 18 years old to get an official driver's license for motorbikes or cars with up to nine seats. Those who are 16 can drive motorbikes with engines under 50 cc without a license.
Last August, four college students were killed in the northern province of Thai Nguyen when one motorbike they were traveling on crashed into the road divider.
Road accidents are a leading cause of death in Vietnam, killing almost one person every hour.
Over 12,600 traffic accidents occurred in the first nine months of this year, killing 5,659 people and injuring more than 9,600, according to the National Traffic Safety Committee.