A toner supply container, detachably mountable to a main assembly of an image forming apparatus, for supplying toner to the main assembly of the image forming apparatus. The toner supply container includes a main body for accommodating the toner; a discharging opening for permitting discharging of the toner accommodated in the main body of the container; a container shutter member for opening and closing the discharging opening, the container shutter member being provided with an engaging portion engageable with a main assembly shutter member provided in the main assembly of the apparatus, wherein the main assembly shutter member is openable and closable relative to a toner reception opening of the main assembly of the apparatus while the container shutter member and the main assembly shutter member are interrelated with each other, and wherein the engaging portion is capable of passing by a position corresponding to the discharging opening; cover seals covers the engaging portion relative to the discharging opening.