Transnational private governance has emerged in multiple issue areas to promote responsible business practices. While most studies assess its rule-setting function, much less research has been done on the compliance-assessment function. This chapter examines the various actors that are involved in this process—auditors, individual assessors and, to a lesser extent, accreditors—and their respective interactions. Using the Marine Stewardship Council as an empirical case, the chapter examines the level of competition among accredited auditors and assessors, and the degree of organizational interdependence. It argues that while the number of accredited auditors has increased over time, the degree of competition is rather limited, while auditors are also much less operationally independent than expected due to the mobility of assessors across auditors. As such, this chapter contributes to the literature on transnational business governance interactions (TBGIs) by providing a micro-level perspective addressing interactions among governance actors within a transnational private governance regime and their potential influence on regime effectiveness.