1920
- Austria (joined 15 December 1920; left 13 March 1938)
- Bulgaria (joined 16 December 1920)
- Costa Rica (joined 16 December 1920; withdrew 22 January 1925)
- Finland (joined 16 December 1920)
- Luxembourg (joined 16 December 1920)
- Albania (joined 17 December 1920)
Read more about this topic: Member States Of The League Of Nations