An exemplary heat dissipation device includes a heat sink, a fan holder, and a fan secured on a front side of the fan holder. The heat sink includes a base having two first fixing ears at its two lateral sides, and fins on the base. An engaging notch is defined in a top end of four of the fins. The fan holder includes a top panel, and two sidewalls extending downwardly from two lateral edges of the top panel. The top panel has a pair of inserting protrusions at a bottom surface thereof. The two sidewalls have two fixing flanges at lower ends thereof. The top panel is partially placed on the front portion of the top ends of the fins, and the inserting protrusions are inserted into the engaging notches of the fins. The two sidewalls abut against two lateral sides of the heat sink, and the two fixing flanges are disposed on the two first fixing ears.