A fan holder used to secure a fan to a heat dissipation device, includes a main body for mounting the fan thereon, a pair of blocking wings and a pair of baffle walls extending from the main body to define a space for receiving the fan therein. The blocking wings each include a pair of locking protrusions engaging in the fan to prevent the fan from moving vertically. The baffle walls each includes a pair of blocking flanges fittingly received in cutouts defied in the fan to prevent the fan from moving horizontally along a lateral direction of the fan holder. The baffle walls engage with front and rear sides of the fan for preventing the fan from moving along a front-to-rear direction.