A mounting mechanism for storage device includes a tray (30) receiving a storage device (20) therein, a bracket (50) attached in the tray, and a chassis (2). An operating unit (10) pivotally attached to the bracket includes an actuator (60), a moveable member (90) and a fixing member (80) disposed in the actuator, and a spring (70) arranged between the moveable member and the actuator. The chassis includes a number of spacing plates (3) each defining a pair of apertures (4). The moveable member includes a pair of wedge-shaped extension tabs (922). The tray is secured in the chassis, with the extension tabs extending through the apertures the chassis. To detach the tray from the chassis, the operating unit is pivoted out and the moveable member is according rotated outward to withdraw its extension tabs from the apertures of the chassis.