An ice tray assembly and a refrigerator having the same are disclosed. The ice tray assembly includes an outer case on which a water container is mounted, and an inner case detachably mounted in the outer case to include ice trays which are supplied with water from the water container. The ice tray assembly includes the inner case which is detachable therefrom, thereby facilitating washing. Further, the ice trays can be supplied with water at once without water leakage and ice cubes made in the ice trays can be separated from the ice trays at once.