Using corporate social responsibility (CSR) ratings for 23,000 companies from 114 countries, we find that a firm's CSR rating and its country's legal origin are strongly correlated. Legal origin is a stronger explanation than “doing good by doing well” factors or firm and country characteristics (ownership concentration, political institutions, and globalization): firms from common law countries have lower CSR than companies from civil law countries, with Scandinavian civil law firms having the highest CSR ratings. Evidence from quasi‐natural experiments such as scandals and natural disasters suggests that civil law firms are more responsive to CSR shocks than common law firms.