An electronic device includes a housing, an expansion card holder, and a protective cover assembly. The housing defines an opening. The expansion card holder is located inside the housing. The protective cover assembly includes a rotary shaft unit, and a cover rotatably connected to the main body via the rotary shaft unit. The cover includes a main body made of soft material, and an elastic member embedded in the main body. The main body includes a cover portion covering the opening, a resisting portion resisting against the housing, and a connecting portion interconnecting the cover portion and the resisting portion. The elastic member includes a first elastic arm and a second elastic arm. The first and the second elastic arms are embedded in the cover portion and the resisting portion, respectively. The elastic member provides a resilient force to the cover portion to open or seal the opening automatically.