A fuel cell system includes at least one fuel cell and a humidifying device for humidifying a supply air flow flowing to a cathode chamber of the fuel cell by an exhaust air flow discharged from the cathode chamber of the fuel cell. The supply air flow and the exhaust air flow are separated from one another by water vapor-permeable membranes. An anode water separator, through which exhaust gas from an anode chamber of the fuel cell flows, is integrated into the humidifying device.