Abstract The concept of institutional isomorphism has made an enduring contribution to sociological theories of organizations, elucidating distinctive ways in which institutional forces such as commonly shared norms and ideas shape organizations. Its core idea is that organizations' concerns for legitimacy constitute a major source of convergence and conformity in organizational forms and practices. Three major drivers of such convergence are identified: external pressure exerted by powerful organizations on dependent organizations to adopt specific forms and practices; conditions of uncertainty compelling organizations to emulate fellow organizations that are perceived to be more legitimate; and increasing professionalization within a sector or field. Institutional isomorphism has been applied to the study of a wide variety of organizations including government agencies, corporations, schools and universities, and nonprofit organizations. Institutional isomorphism's emphasis on convergence and conformity is seen to be limiting when it comes to accounting for more proactive and strategic kinds of organizational response to environmental conditions.