An image forming apparatus includes a plurality of developer containers to contain different types of developers and a container mount in which the plurality of developer containers is removably installed and arranged adjacent to each other. Each of the developer containers includes an engagement portion. The engagement portion of one of the developer containers engages the engagement portion of another of the developer containers adjacent to the one of the developer containers when the developer containers are installed in the container mount in a predetermined order, to allow the developer containers to be installed. Further, the engagement portion of one of the developer containers interferes with the engagement portion of another of the developer containers adjacent to the one of the developer containers when the developer containers are installed in the container mount in a different order from the predetermined order, to prevent the developer containers from being installed.