A hard disk drive (HDD) module includes a bracket with two opposite sidewalls, an HDD, and a positioning element rotatably mounted between the sidewalls of the bracket. Each sidewall defines a leading slot and a latching slot communicating with the leading slot. Two blocks extend from opposite sides of the HDD. When the blocks enter the corresponding leading slots, the latching element is rotated to push the HDD to move, with the blocks moving into engagement with the corresponding latching slots, to assemble the HDD in the bracket.