Provided are a disk spacer for an information storage device and a spindle motor assembly employing the disk spacer. The spindle motor assembly includes a spindle motor, one or more data storage disks mounted around the spindle motor, a disk clamp coupled to the spindle motor and fixing the disk clamp, and a disk spacer mounted around the spindle motor and supporting the disk, wherein the disk spacer has a groove of a predetermined depth formed along an outer peripheral surface thereof, which does not contact the disks, and the groove is tapered as it is closer to an inner peripheral surface of the disk spacer away from the outer peripheral surface of the disk spacer. Since impacts and vibrations delivered to the disks are scattered by the disk spacer, the wobble of the disk due to the impacts and vibrations is reduced.