A heat dissipation device includes a heat sink, a retention module and a clip securing the heat sink to the retention module. The retention module includes a bottom wall and a plurality of sidewalls surrounding the bottom wall. The heat sink includes a plurality of the fins and a plurality of passages defined therebetween. The heat sink is located on the bottom wall of the retention module. The sidewalls of the retention module surround a bottom portion of the heat sink. The sidewalls define a plurality of voids therein for an airflow generated by a fan mounted on the heat sink passing therethrough. The airflow flows through the heat sink and then the voids in the sidewalls of the retention module to cool electronic components located beside the retention module.