When statements made before the Iran-United States Claims Tribunal (the ‘Tribunal’) have exhibited some degree of divergence from representations or conduct made at a different point in time, estoppel and associated concepts have often proved to be of considerable assistance in determining between the competing versions presented. This article will assess the application of the doctrine of estoppel and related concepts by the Tribunal and compare its jurisprudence with the position of such principles as accepted in international law.