Over the course of three centuries, the institutional organisation of the Christian church evolved from small, loosely organised groups meeting in house churches to a form of hierarchical organisation known as monepiscopacy. Monepiscopacy denotes a form of ecclesial polity in which a single bishop possesses authority over the church and oversees the administrative responsibilities of that church as head of its ministry. This paper develops a theory that explains why the early Christian church ([Formula: see text]33CE–325CE) would choose monepiscopacy as a form of church polity. Specifically, we argue that monepiscopacy was an efficient governance framework for solving collective action problems, establishing legitimacy, screening high-effort converts, and constraining socially costly behaviours. Drawing upon the tools of rational choice theory and previous work in institutional economics, we argue that hierarchy helped the early church monitor and punish free-riding, coordinate around orthodox doctrine, and screen potential converts.