A heat dissipation assembly includes a heat sink (20), a backplate (50), a pair of posts (60) and a fastener (10). The heat sink is attached on a CPU (30) which is mounted on a PCB (40). The backplate is disposed below the PCB. The fastener includes a main body (14) spanning on the heat sink, a resilient member (16) and an operating member (12). The posts extends through the backplate and engaged with the main body. Before the fastener is activated, the resilient member and the operating member squeezes the main body therebetween. When the fastener is activated, the operating member is above the main body. The resilient member resiliently presses the heat sink toward the CPU and the main body with opposite directional forces. The posts are consequently forced by the main body to urge the backplate against the PCB.