A portable, self-contained vehicle seat occupancy alert device alerts a person (e.g., the vehicle operator) upon exiting a vehicle seat. The alert serves to remind the person of the presence of passengers or cargo upon the person exiting the vehicle. The alert device comprises a pad placed between a person and the vehicle seat. One or more pressure sensors disposed within the pad are operative to detect the presence or absence of a person in a vehicle seat. An alarm is armed upon a sensor detecting the presence of a person in a vehicle seat, and is operative to emit a warning upon a sensor detecting the absence of the person from the vehicle seat. Thus, wherever the person exits the vehicle seat, the alarm emits a warning, reminding the person to check for passengers or cargo that needs to be removed from the vehicle.