A device for simultaneously filling a container serving as a fuel tank and a container serving as a reducing-agent container with a single pump nozzle is used for environmentally friendly internal combustion engines with exhaust-gas purification systems requiring both tanks which are to be refilled repeatedly. Filler necks of the containers as well as outlet pipes disposed in the pump nozzle and assigned to the filler necks, are combined. A method for filling the containers is also provided.