Curiously, international legal scholars closely examine the ‘practice’ of international law, yet they rarely study international legal practices. This chapter reviews – and advocates for – the application of sociological theories of ‘practice’ to the study of international law. Practice theory provides a conceptual framework and analytic tools that enable scholars to identify and understand the complex social practices whereby international law is made, interpreted, and applied in the contemporary world. Following a brief introduction to practice theory, this chapter traces the movement of practice theory to the international level in international relations theory, and examines the much more recent and tentative adoption of practice approaches by international legal scholars. The chapter then focuses on international judicial practices, and reviews efforts to describe and explain the large number and variety of practices that have arisen in and around international courts and tribunals. The chapter briefly addresses epistemological and methodological questions of how best to access and study of international legal and judicial practices that often take place outside of public view. A brief conclusion outlines an agenda for future research in this young and rapidly developing field of study.