A developer cartridge includes a developer roller, a support member and a first seal member. The developer roller has a rotational axis and a peripheral surface. The peripheral surface includes a center zone and an end zone at one end portion in an axial direction. The support member supports the developer roller to be rotatable about the rotational axis. The support member has an opposing surface opposed to the end zone. A protrusion protrudes from the opposing surface, and extends in a direction crossing with the axial direction. The first seal member is disposed between the end zone and the opposing surface in order to prevent developer from leaking out of a space formed between the end zone and the opposing surface.