Recent research suggests that corporate social responsibility (CSR) is institutionalised amongst multinational corporations. Yet CSR scholarship faces considerable challenges. An agreed definition is lacking, even amongst researchers adopting aligned approaches. Studies remain heavily focused on making a business case for CSR, despite its widespread acceptance into business practice. Few studies examine CSRâ€™s on-ground implications for the communities it purports to help, favouring instead a macro-level focus. And concerns about CSRâ€™s sincerity, motivations and ethics perpetuate questions about its integrity. This article argues that new institutionalism is well placed to respond to these core challenges for CSR, and that new institutionalist perspectives can complement and enrich other common theoretical approaches. It contributes a social mechanism-based framework for CSR, identifying and exploring the key social mechanisms that institutionalise it; namely, discourse, mimesis, normative learning and coercion. Understanding CSR as an institution facilitates new and different explorations of its causes and effects and opens new avenues for scholarly inquiry. Illustrative examples from a 3.5-year study of CSR in the global mining industry are presented to explore the implications of CSR as an institution and to suggest pathways for innovative research.