A vehicular electronic key system includes an electronic key and a wireless communication device. The electronic key includes a first communication unit, a second communication unit, and a first controller that switches an operating state between an ON state where a function of the first communication unit is operated, and an OFF state where the function of the first communication unit is at least partially stopped, based on a result of communication of the second communication unit with the wireless communication device. The wireless communication device includes a third communication unit, and a second controller. The first controller switches the operating state when the first controller detects that the electronic key has been moved by a predetermined distance or longer outside a vehicle based on at least a result of communication of a predetermined signal by the second communication unit.