This paper suggests a new framework for the legitimacy of international adjudication relative to other branches and modes of public decision-making. Named ‘Public Epistemic Authority’, this new framework approaches judicial authority from its often-overlooked institutional dimension. In this dimension, the collective decision-making setting of international courts must find its due consideration. The paper draws on the mechanisms of collective wisdom popular with epistemic theories of democracy to establish a truth-tracking benchmark for international adjudication. Based on this benchmark, the paper suggests an epistemically improved institutional design of international courts and formulates several epistemic principles for judicial reasoning.