The car seat occupancy alarm is an alarm that detects the presence of individuals seated in the rear of the vehicle, and upon detection of which shall emit an alarm, provided the vehicle is turned off. The alarm system includes pressure sensors that are integrated into the rear seats of a vehicle, and which are in wired communication with a central processing unit located elsewhere within said vehicle. The central processing unit is further in wired communication with a timer, vehicle lights, and a vehicle battery in order to operate, sense, and emit an alarm upon detection that individuals remain in any of the rear seats while the vehicle is parked.