A heat dissipation device includes a heat sink (10), thermal interface material (30) spread on a bottom surface (16) of the heat sink, two legs (22) of a clip (20) disposed at opposite sides of the heat sink, and a protective cap (40) enclosing the thermal interface material therein. The protective cap includes ears (48) interlocked with the legs of the clip to retain the protective cap to the heat sink. The legs of the clip are also used for interlocking with engaging member (52) on a printed circuit board (50) thereby firmly mounting the heat sink to a CPU (54) on the printed circuit board.