This article examines corporate social responsibility (CSR) pertaining to labor standards in apparel and tax transparency in extractives and explores how domestic regulatory traditions shape CSR in large international US and UK firms. Reflecting their more collaborative business-government traditions, British firms are more willing to join international CSR multi-stakeholder initiatives with business-critical actors such as unions and civil society actors. The US has a more top-down regulatory approach, which promotes hard law international CSR or encourages business-driven voluntary CSR initiatives. This article makes three contributions. First, it argues that while corporations are the key actors in international CSR, their behavior reflects their respective national business systems. Second, focusing on a range of international CSR initiatives, this article finds that UK firms are more interested in adopting international (multi-stakeholder) CSR initiatives than US firms. Finally, the article shows that the US and the UK governments play a key role in driving an international CSR agenda, and in doing this it highlights government agency more so than other research has.