A developer cartridge includes a container having a developer discharge opening, and a table formed around the discharge opening. A slidable plate-shaped lid is slidably mounted on the table, and the lid includes first and second lid portions which are interconnected to each other. A film member is attached to the table and is peelably adhered around the discharge opening. The film member includes a sealing portion for closing the discharge opening, and a second portion folded back over the sealing portion. The second portion extends through the gaps between the first and second lid portions. A grip is fixed to a free end of the second portion of the film member and is provided with an urging portion releasably engaged with a plate surface of the lid.