A motor-driven compressor that includes a compression unit adapted to compress refrigerant, an electric motor adapted to drive the compression unit, and a housing that accommodates the compression unit and the electric motor and includes a coupling member. A motor driving circuit drives the electric motor. The motor driving circuit includes a circuit board and a capacitor, which is electrically connected to the circuit board. A capacitor holder holds the capacitor and is coupled to the coupling member. One of the capacitor holder and the coupling member includes a projection, and the other one of the capacitor holder and the coupling member includes an engagement portion that engages with the projection. Engagement between the projection and the engagement portion positions the capacitor holder relative to the coupling member.