Abstract: A heat sink assembly includes a clip (10), a heat sink (50), and a retention module (60). The clip has two main bodies (20) and a beam portion (40). The beam portion includes a top plate (42), a side plate (44), and a connecting plate (48). Two through slots (49) are defined in opposite ends of the connecting plate (48). Two mounting slots (43) are defined in opposite ends of the top plate. Each main body includes a first leg (26), a central pressing portion (22), and a connecting portion (28). The connecting portion passes through a corresponding through slot, and is snappingly received in a corresponding mounting slot. Two recessed portions (56) are defined at opposite sides of the heat sink. The pressing portions are for pressing on the recessed portions. The retention module engagingly receives the first legs, and second legs of the beam portion.