A heat dissipation device includes a heat sink (10) and a fan (30) mounted on the heat sink via a pair of fan holders (20) and clips (40). The fan holders each have a supporting plate (24) attached on the heat sink and a sleeve (26) connected to the supporting plate and spaced from the supporting plate. The fan has upper and lower flanges (32, 34). The lower flange is sandwiched between the sleeve and the supporting plate. The clips each include a shaft (42) extending through the sleeve, a spring (44) mounted around and received in sleeve, and a handle (46) pivotably mounted on the shaft and movable between unlocked and locked positions. When the handle is positioned at the locked position, the shaft is inserted in the lower flange of the fan to thereby secure the fan on the heat sink.