A fan holder is used for securing a fan to a heat sink. The fan holder includes a cover mounting the fan thereon, and a base mounting the cover thereon. The cover includes a plurality of separate claws and at least one jut. The base includes a through hole receiving the claws of the cover therein, thereby rotatably mounting the cover onto the base, and at least one slot. The at least one slot has a first pit and a second pit at two ends thereof respectively. The at least one jut is slidable along the slot between the first pit and the second pit to have the cover rotatable between a first location and a second location.