The right to be heard is well known as a fundamental right of the European Union legal order. Less well known is its relation to customary international law predating international human rights law. This paper sets forth two arguments. First, the right to be heard enshrined in the Charter of Fundamental Rights of the EU must be interpreted in conformity with the right to be heard as protected under the customary international minimum standard of treatment of aliens. Second, the latter standard implies that the right to be heard is an emanation of the broader concept of adjudicatory transparency, which is a primary aspect of the rule of law, with the extended implication that the right to be heard serves to enable individuals to participate in and influence adjudicatory decision-making by engaging in a rational dialogue with the decision-making authority.