A developer container is detachably mountable to a developer replenishing apparatus and includes a cylindrical accommodation member for accommodating a developer and a coupling portion for engaging with a main assembly coupling portion provided on the developer replenishing apparatus by movement in an inserting direction. In addition, a contact portion contacts an urging portion in the developer replenishing apparatus and receives a push-off force from the developer replenishing apparatus in a direction opposite to the inserting direction, and an engaging portion is engageable with an opening and closing portion provided in the developer replenishing apparatus to receive a force from the opening and closing portion in the inserting direction and against the push-off force in a closing operation of the opening and closing portion when the developer container is inserted into the developer replenishing apparatus.