Abstract: A heat sink assembly includes a heat sink and a clip. The clip includes a main body, two pressing portions extending outwardly from two opposite ends of the main body, two extension portions each extending upwardly from an outer end of a corresponding pressing portion, a locking arm extending slantwise and upwardly from an upper end of each extension portion, a U-shaped operating portion extending from a far end of the locking arm and a J-shaped hook extending from a free end of the operating portion. The operating portion is provided for receiving a depressing force acting on the clip for moving the hook to engage with a clasp on a printed circuit board.