How can regulatory agencies with a technical or scientific mission forge and defend their reputation, when the definition of expertise is subject to countervailing influences and perceptions among a wide array of audiences? In this paper, we tackle this broad question, focusing on a particular episode of the European controversy over the regulatory control of exposure to bisphenol A, during which the European Food Safety Authority altered the method by which it produced an assessment of the risk of BPA, responding to the regulatory controversy surrounding this substance. Building on the literature on organizational reputation and science and technology studies, we shed light on the work that regulatory agencies undertake to gain credibility in particular configurations of audiences. This perspective on the management of audiences and knowledge standards is central for the explanation of the decisions, policies, and strategies of science‐based agencies, and the way in which a technical reputation takes form in controversy‐prone areas of regulation.