A heat dissipation device includes a heat sink, a fan mounted on a top side of the heat sink, and a wire clip pivotally engaging with the heat sink and pressing the fan toward the heat sink. The heat sink includes a base, and a plurality of fins extending from the base. The fan includes a bracket. The clip includes a pivoting portion pivotally engaging with a fin of the heat sink, an engaging portion connecting with an end of the pivoting portion and an operating portion extending from another end of the pivoting portion. The operating portion is pressed downwardly to engage with the heat sink and to cause the engaging portion to rotate towards the fan and press the bracket of the fan toward the heat sink thereby securing the fan to the heat sink.