Occupants prefer different seating postures with different seatback angles. With the development of autonomous cars, there will be diverse settings for the seatback angle. This paper investigates the effect of seatback angle on whiplash risk in forward facing front seats. For this purpose, a volunteer was seated in a typical car seat with recliner adjustment and the volunteer was asked to assume a comfortable driving posture at seatback angles of 15, 20, 25 and 30 deg from the vertical. Rear impact simulations were run comprising a 50th percentile male human-body model (having the posture of the volunteer) seated in a state-of-the-art whiplash-mitigating car seat with different initial seatback angles. The seat-occupant simulations show that for all seatback angles, the whiplash mitigating seat gets maximum points from all ten whiplash assessment criteria in EuroNCAP whiplash protocol with the exception that NIC value for 30 deg seatback angle is close to the higher (good) performance limit. It is observed that whiplash risk increases with larger seatback angles therefore it is not advised to use seats with larger seatback angles.