A developer supply container substantially non-rotatably mountable, with a developing device, to a rotatable member provided in an image forming apparatus, said developer supply container being adapted to supply a developer into the developing device therefrom with rotation of the rotatable member, said developer supply container includes a container body for containing the developer; a discharging opening, formed in a peripheral surface of said container body, for permitting downward discharge of the developer; a feeding portion, provided in said container body, for feeding the developer in a feeding direction toward said discharge opening with rotation of said rotatable member; and a developer movement constraining portion, provided adjacent a position facing said discharge opening within in said container body, for constraining the developer which is reversed into said container body through said discharge opening when said discharge opening faces upward with rotation of said rotatable member, from moving in a direction opposite to the feeding direction.