An exemplary heat dissipation fan includes a housing and an impeller. The housing includes a casing. The casing includes a bottom wall and a side wall extending upwardly from the bottom wall. The impeller is received in the housing. The impeller includes a hub and a plurality of blades extending radially and outwardly from the hub. Each blade has a distal end facing the side wall of the casing. The inner side of the side wall depressed towards an outer side of the casing.
