A data storage device mounting apparatus includes a base, a securing member, and a cover engaged with the base. The base includes a receiving portion and a recess, the recess defines a through hole. The securing member is secured to a first data storage device and includes a securing piece. The securing piece defines a stopping hole. The cover is configured to cover a second data storage device. A stopping portion located on the cover. The receiving portion is adaptor to receive the first data storage device, the securing piece is received in the recess, and the stopping portion extends through the through hole to engage in the stopping hole, for preventing the first data storage device from disengaging from the receiving portion.