A heat sink adapter for cooling an electronic component includes a lower plate, an upper plate fixed on the lower plate, and a plurality of heat pipes sandwiched between the lower plate and the upper plate. The lower plate includes a panel, a pair of sidewalls extending upwardly from two opposite sides of the panel, and a plurality of flanges extending upwardly from the sidewalls, respectively. The upper plate defines a plurality of cutouts corresponding to the flanges. The flanges fit into the cutouts to position the upper plate on the lower plate, whereby the lower plate and the upper plate are mechanically connected together.