A memory module assembly includes a printed circuit board (10) having a main heat-generating electronic component (52) thereon, first and second heat sinks (20), (30) attached on opposite sides of the printed circuit board and a clamp (40) clamping the first, second heat sinks and the printed circuit board together. The first heat sink comprises a pair of positioning poles (24). The second heat sink comprises a heat pipe (36) disposed therein and thermally connecting therewith. The clamp comprises a connecting portion (42) and a pair of elastic pressing portions (44). The clamp resiliently presses the second heat sink toward the main heat-generating electronic component and the first heat sink engages with the second heat sink via the positioning poles of the first heat sink extending in and engaging with the second heat sink.