The victims from Bodinayakanur were returning from a pilgrimage to the famous hill shrine of Lord Venkateswara at Tirupati when the mishap occurred, police said.
The driver apparently lost control of the car which then hit the road median and was thrown into a ten-foot deep ditch, killing Iswarya (26) and her son Ranjan on the spot.
The injured had been admitted to a private hospital in Salem.