The car, with a driver and three passengers, was trying to pass the tracks at a crossing in Tuy Phong District in the south central province at around 9 a.m. when it was hit by a southbound train.
The car was pushed on the track for more than 200 meters before being flung aside into a nearby rice field.
"The 32-year-old driver of the car, Nguyen Thanh Truc, and two passengers, including a 10-year-old girl, died on the spot while another was seriously injured and taken to local hospital but succumbed to injuries later," a local official said.
There is a warning signal at the level crossing, which does not have a guard.
Earlier this month, two taxi passengers were killed when their car was hit by a train at a level crossing in the central Quang Ngai Province.
Official statistics shows about 267 railroad incidents occurred across the country last year, down 22.8 percent over 2017. 124 people were killed and 184 others injured.
According to the Vietnam Railways Corporation, there are 5,793 level crossings in the country. Of these, only 641 have stationed guards, 366 have automatic alarms and 507 have warning signs.