A developer supply container is detachably mountable to a developer receiving apparatus, the developer receiving apparatus including a developer receiving portion provided with a receiving port for receiving a developer and including a portion-to-be-engaged capable of displacing integrally with the developer receiving portion. The developer supply container includes a discharging portion provided with a shutter opening for discharging the developer accommodated in the developer accommodating portion, and an engaging portion. The engaging portion engages with the portion-to-be-engaged with a mounting operation of the developer supply container to displace the developer receiving portion so as to bring the receiving opening into fluid communication with the shutter opening. The engaging portion includes a curved portion having an angle relative to a mounting direction of the developer supply container, the angle decreasing with approach toward an upstream side in the mounting direction.