This chapter contains an analysis of the most appropriate way to determine the applicable attorney–client privilege standard in international commercial arbitration. To this end, this chapter deals with the characterization of privilege as substantive or procedural, the legal framework for attorney–client privilege in international commercial arbitration, international mandatory rules of law, and the enforcement regime under the New York Convention on the Recognition and Enforcement of Foreign Arbitral Awards of 1958. Against this background, the chapter includes an analysis of the possible approaches to determining the privilege standard. These include the application of general principles of law, the application of a single national law determined through a choice-of-law approach such as the closest connection test, the cumulative application of several national laws, and the creation of an autonomous standard defining the scope of attorney–client privilege. Lastly, the chapter examines whether corrective measures, such as the lowest common denominator approach or the most protective rule, are needed to ensure equal treatment of the parties and fairness of the proceedings. This chapter concludes with key findings on how to determine the applicable attorney–client privilege standard in international commercial arbitration.