An infant seat alarm system to both detect and alert the presence of an unattended infant in a vehicle comprises an infant seat having a sensor and a detector seat having a second sensor. The sensor is coupled to the second sensor and both sensors are coupled to a timer device. A power supply independent of a power supply of the vehicle powers the timer device. One or more alarms are coupled to the timer device. After a predetermined time the timer device actuates at least one of the alarms to emit an audible sound if the infant seat is occupied by an infant and the detector seat is unoccupied by a person. An external alarm may be coupled to the timer device. Additionally a switch operable by a person may be coupled to both the timer device and the sensor of the infant seat.