The incident occurred on Saturday evening in Cheo Bau Village, Gia Phu Commune. At around 7 pm, residents alerted authorities after a motorbike was found stranded in a stream.
About an hour later, the family identified the vehicle and reported that a 14-year-old girl, who had been riding the motorbike with her two younger siblings, aged five and three, had not returned home.
Rescue teams searched along the stream and nearby areas overnight before recovering the bodies of all three children on Sunday morning.
Local authorities are assisting the family with funeral arrangements.
The National Centre for Hydro-Meteorological Forecasting said scattered showers and thunderstorms, with isolated heavy rain, are expected to continue across northwestern Vietnam on Saturday, with risks of lightning, hail and strong winds.