A warning lamp assembly includes a housing having an upper chamber and a bottom chamber; a driving unit; a gear mechanism including a rotary disk disposed within the upper chamber, and formed with an inwardly and radially extending retention flange, a bearing unit disposed on the retention flange so as to permit rotation of the disk relative to the upper chamber, a toothed wheel having outer peripheral teeth meshed with an axle of the driving unit and an inner periphery formed with downward projections slidably contacting the bearing unit and hence covering the same from above to prevent disengagement of the wheel from the rotary disk; a light source fixed within the upper chamber; and a parabolic reflector disposed on the wheel and covering the light source from above to reflect light rays emitted from the light source in a horizontal plane while simultaneously rotating together with the wheel.