This chapter 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.The principle of equal treatment or procedural equality is a core adjudicative ideal that has a long history dating as far back as the Magna Carta Libertatum. Together with the right to an impartial and independent tribunal and the right to be heard, the principle of equal treatment provides a foundation for the arbitral process that is essential to ensure its legitimacy. The principle of equal treatment pervades every aspect of the arbitral process and must be given due regard at each stage of the proceedings: at the stage of tribunal constitution, when joining additional parties, allocating time, determining the scope of privilege or allowing non-disputing third parties to intervene, among others. While the importance of procedural equality in international arbitration is today well-established, less attention has been paid to how claims of equality ought to be assessed. Drawing on jurisprudence on equal treatment protections in international human rights law, this chapter proposes a two-step inquiry that first considers whether there is a rational basis for any differentiated treatment between the parties, before analysing whether the differentiated treatment creates an unfair disadvantage.