A tailgate controlled light system for automatically illuminating the interior of a pickup box upon opening of a tailgate. The tailgate controlled light system includes a light unit attachable within a pickup box, a control switch electrically connected to the light unit and attachable within the opening of the pickup box, and an override switch electrically connected to the control switch and to the vehicle power supply. The control switch is positioned to be depressed by the tailgate when closed thereby terminating power to the light unit. When the tailgate is opened away from the control switch the light unit is activated with power. The override switch is used to terminate power to the light unit regardless of the position of the tailgate.