A parking assist system includes: a control device configured to control an autonomous parking operation to move a vehicle autonomously to a prescribed target parking position; and a vehicle state detecting device configured to detect a state of the vehicle. During control of the parking operation, when the control device determines that the state of the vehicle detected by the vehicle state detecting device is a prohibition state in which the parking operation should be prohibited, the control device executes a prohibition deceleration process to decelerate the vehicle so as to stop the vehicle. The control device is configured to set an upper limit on deceleration of the vehicle in the prohibition deceleration process to be larger than an upper limit on deceleration of the vehicle in a stop operation to stop the vehicle at the target parking position.