An illuminated toy construction kit includes a plurality of illumination modules having various shapes and sizes, and a plurality of non-illumination modules having different shapes and sizes. Each of the illumination modules includes at least one light-emitting element, such as, for example, a color-varying LED. At least some of the non-illumination modules are in the form of couplers which function as mechanical linkages for interconnecting the illumination modules and enabling a user to form a variety of three-dimensional structural shapes. The couplers also function to transmit electric power between the interconnected illumination modules, whereby all of the interconnected modules may be simultaneously illuminated in response to the activation of a single power source connected to at least one of the illumination modules.