A heat sink fastener includes a main body, a piercing member and a wire clip. The main body includes a pressing part for holding a heat sink in contact with a heat-generating component, an engaging part and a latching leg; the engaging part and the latching leg are disposed at opposing ends of the pressing part. The piercing member includes a piercing body extending through the engaging part of the main body and a tubular part and a hook. The wire clip includes a pivot shaft pivotally connected with the tubular part of the piercing member, a locking leg for fastening to the main body and a lever interconnecting the pivot shaft and the locking leg together, wherein the lever is rotatable to change the positional relationship between the piercing member and the engaging part of the main body.