This article examines a particular mode of agri‐food governance: international food standard setting. Sociological accounts of technical regulatory processes such as standard setting can help to illuminate the role of expertise in the governance of the agri‐food system. Firstly, the potential contribution of the concept of epistemic communities to the analysis of international food standard setting is discussed. Secondly, the article details the architecture of international trade regulation and the operational procedures of the Codex Alimentarius Commission (the Codex), the intergovernmental organisation in which international food standards are set. Thirdly, the role of scientific expertise to the standard setting process in the Codex is explored through a case‐study of the attempt to establish an international definition for dietary fibre. The article concludes by reflecting upon the importance of contestation over knowledge claims to the conduct of agri‐food governance.