Abstract: A vehicle child seat safety system comprises a child seat sensor connected to a transmitter, a receiver in the vehicle connected to a processor controlling exterior lights, ignition switch, air conditioner, alarm and door locks, to advise a driver and passersby of a child left in the vehicle unattended, and provide for the access to the vehicle. The application is further directed to a method of informing of a child left unattended in a locked vehicle comprises providing a sensor in a child seat, starting the sensor when the ignition is turned off, generating a warning signal and transmitting same from a transmitter in the child seat after a predetermined time elapsed since starting the sensor, receiving the signal in the vehicle to direct a CPU of the vehicle to start an alarm sound signal and turn alarm lights on, and, if the sensor is not disabled, to further unlock door locks and start air conditioner.