A heat sink assembly includes a base plate, a fin group and a heat pipe thermally connecting the base plate with the fin group. The fin group includes a plurality of fins. The heat pipe includes a straight evaporating section contacting with the base plate, a first condensing section extending upwardly from an end of the evaporating section and through the fins, a second condensing section bent downwardly from a free end of the first condensing section and through the fins, and a third condensing section extending upwardly from an opposite end of the evaporating section and through the fins. Periphery walls of at least two of the first, second and third condensing sections substantially totally contact with the fins to increase a contact area between the heat pipe and the fins.