The car driven by a man suddenly turned into the opposite lane in Cua Duong Commune and collided heads-on with three motorbikes, which were badly damaged.
A man and his eight-year-old daughter on one motorbike died after being rushed to hospital. Four people on two other motorbikes were injured.
The car driver left the scene after the crash.
Two more deadly car crashes occurred in Phu Quoc, a popular tourist island, over the past five days.
A car hit a motorbike driver and killed him on Saturday night. Four days earlier, another car was turning into a house when it hit and killed a boy playing on the sidewalk.