This study examines the relationship between board co-option and corporate social responsibility (CSR) among U.S. firms. The results indicate that higher levels of board co-option are linked to weaker CSR performance, particularly in terms of environmental initiatives and diversity-related social programs. The negative association between board co-option and CSR is more pronounced in firms in which CEOs hold substantial power and short-term managerial compensation is prioritized and in industries characterized by higher information asymmetries. In contrast, independent, non-co-opted directors appointed before the incumbent CEO enhance engagement in CSR, highlighting their important role in fostering socially responsible corporate behavior.