A toner cartridge contains a toner container including an opening and configured to contain a toner. An engaging member includes a ring-shaped seal member disposed on a seal member installation surface. The engaging member is engaged with the toner container to cover the opening and rotatably mounted to the toner container while an edge of the opening is frictionally slid on a surface of the seal member. The toner container is configured to convey the toner into the engage member through the opening and discharge the toner therefrom as the toner container is rotated. The seal member includes a non-contact portion at a surface thereof facing the installation surface and being free from any contact with the installation surface so that the engage member includes a space extending from the surface of the seal member where the edge of the opening is frictionally slid to the non-contact portion.