A developer cartridge includes a developer container, an agitating member, a first shutter, and a first rotatable member. The developer container includes a first arc-shaped wall having an arc shape that is concave inward in a cross-sectional view. A first opening is formed in the first arc-shaped wall. The agitating member is positioned in the developer container and configured to agitate the developer. The first shutter has an arc shape in the cross-sectional view and is configured to rotate along a periphery of the first arc-shaped wall between a first position to open the first opening and a second position to close the first opening. The first rotatable member is positioned at at least one axial end of the first shutter. The first shutter is configured to rotate in response to rotating of the first shutter.