A collision object protection assembly inflates and expands an air bag on a vehicle if a collision with the vehicle is detected or predicted. The collision object protection assembly includes a retainer positioned in a space between a bonnet hood and a front window glass of the vehicle and accommodating the air bag, and a cowl top arranged around the retainer to close the space between the bonnet hood and the front window glass. The retainer has an upper opening to be covered by a lid member. The lid member is a separate member from the cowl top.