The principle of equal treatment is fundamental to the idea of justice, in international arbitration as in any adjudicative system. Arbitration conventions, rules and national laws unanimously impose a requirement, either express or implied, that the parties be treated equally throughout the arbitral process. Yet, the contours of procedural equality remain elusive. Defining procedural equality is indeed arduous, in no small part because it is inherently fact sensitive. Nevertheless, such definitional challenges should not preclude a more sustained analysis on the role that equal treatment plays in international arbitration, nor should it dissuade attempts to discern a methodology for its analysis. This paper offers a contribution to the discourse on procedural equality in international arbitration by explaining its interaction with other basic norms that govern the arbitral process and proposing a framework to assess equality claims. Part I of the chapter outlines the origins of the equal treatment principle in international arbitration. Part II identifies the key aspects of the arbitral process where procedural equality concerns are likely to arise. Part III conceptualizes the equal treatment principle as a core adjudicative ideal that, together with the right to an impartial and independent tribunal and the right to be heard, provides the foundation for legitimacy of the arbitral process. Part III also draws on jurisprudence on equal treatment protections in international human rights law to propose a methodology to assess procedural equal treatment claims in international arbitration. Finally, Part IV provides some concluding observations.