A developer storage container includes a container body, an opening formed in the container body, an opening-and-closing cover, a cover holding frame that holds the cover so that the cover is movable between opening and closing positions, a protrusion portion, a blocking portion and a position regulating protrusion. When the opening-and-closing cover moves in the opening-and-closing direction toward the opening position and reaches a certain intermediate position, the blocking portion contacts with the protrusion portion. When the opening-and-closing cover moves from a position where the protrusion portion and the blocking portion are in contact with each other to the closing position, the position regulating protrusion causes the opening-and-closing cover to move in a intersecting direction and regulates a position of the opening-and-closing cover in the intersecting direction so that the blocking portion is overlapped, along the opening-and-closing direction, with the position of the distal end of the protrusion portion.