An assembly includes an electronic device casing, a heat-dissipating module and a waterproofing module. The electronic device casing is formed with an encircling wall. The encircling wall has a wall body and an apertured portion formed in the wall body. The heat-dissipating module is coupled to the electronic device casing, is surrounded by the encircling wall, and includes a heat pipe extending through the apertured portion. The waterproofing module includes a waterproofing element that has a ring portion disposed on a top rim of the wall body, and a sleeve portion having a first sleeve segment that is connected to the ring portion, that is sleeved on the heat pipe and that engages the apertured portion so as to establish water tightness between the heat pipe and the apertured portion.