The car was headed from Mori to Purola this afternoon when the mishap occurred near Rama bend, an especially accident- prone area, police said.
The car fell into a 150m gorge as the driver tried to negotiate a sharp curve, killing three occupants of the vehicle on the spot and leaving two injured.
One of the injured persons later succumbed during treatment at a hospital in Uttarkashi, police added.
The deceased have been identified as SSB jawan Chatar Singh (42), his 22-year-old daughter Anita, Jagat Singh (52) and Roshan Lal (38).