An electronic device with an airflow guiding duct includes a chassis, an airflow guiding duct, and a top cover. The chassis includes a bottom wall and a sidewall perpendicular to the bottom wall. A circuit board is mounted on the bottom wall. A pair of securing members protrudes from a top of the sidewall. The airflow guiding duct includes a top wall and a plurality of securing slots defined in the top wall corresponding to the securing members, for the securing members being lockingly engaging in the securing slots, thereby limiting movement of the airflow guiding duct in directions parallel to the circuit board. The cover is mounted on the chassis and abuts against the top wall of the airflow guiding duct, for limiting movement of the airflow guiding duct in a direction perpendicular to the circuit board.