Management researchers have investigated how corporate governance mechanisms influence corporate social responsibility (CSR). The previous literature has been largely based on agency theory, which emphasizes the roles of effective monitoring and incentive alignment, but the empirical evidence has been mixed. This inconsistency may result from the assumption that each governance mechanism functions independently, even though they interact with one another to affect CSR. On the basis of a perspective of bundle of governance mechanisms, we examined whether multiple governance mechanisms act as complements or substitutes for each other in promoting CSR. Using a panel sample of U.S. firms for the years 2004 to 2010, we found that multiple governance mechanisms mainly act as substitutes to promote CSR. Our findings suggest that a similar level of CSR can be achieved with different combinations of governance mechanisms. Our study contributes to the fields of both corporate governance and CSR in theory and practice.