This article examines the mechanisms underlying the worldwide diffusion of organizational practices. We suggest that the two main theoretical explanations in the diffusion literature, efficiency and legitimation, can be complementary. More specifically, we argue that endogenous forces seek to enhance the efficiency of existing systems, while exogenous forces seek to increase legitimation. To assess our argument, we explore the worldwide diffusion of codes of good governance. These codes are a set of ‘best practice’ recommendations regarding the behavior and structure of a firm’s board of directors issued to compensate for deficiencies in a country’s corporate governance system regarding the protection of shareholders’ rights. We have collected data on codes of good governance for 49 countries. We operationalize efficiency needs in terms of the characteristics of shareholder protection, and legitimation pressures in terms of government liberalization, economic openness, and presence of foreign institutional investors. Our analysis supports the argument that both efficiency needs and legitimation pressures lead to code adoption. In addition, our empirical results show that countries with legal systems with strong shareholder protection rights tend to be more prone to develop codes, possibly for efficiency reasons. This article contributes to organization theory by illustrating that he diffusion of codes fosters both cross-national corporate governance convergence as well as some degree of country hybridization, particularly depending on the type of code issuer.