A projector assembly includes a projector casing and an auxiliary device. The projector casing is formed with a mating aperture, and has a first light source for emitting light beams defining an optical path of the projector assembly. The auxiliary device includes a mating part inserted detachably into the mating aperture in the projector casing, a second light source disposed in the mating part for emitting light beams, and a light-beam guiding module disposed in the mating part in front of the second light source so that the light beams emitted from the second light source are guided into the optical path via the light-beam guiding module, thereby enhancing illumination of the optical path of the projector assembly.