Corporate social responsibility (CSR) reporting is becoming increasingly relevant in light of modern corporate governance. There is growing activity among empirical research in one-tier systems that considers the link between board composition and CSR reporting. This study is the first of its kind on the German two-tier system with special regard for the supervisory board. We analyze gender diversity, expertise, the presence of former managers, frequency of meetings, and the size of the supervisory board. Our multiple regressions indicate that gender diversity has a positive impact on CSR disclosure intensity, which is in line with prior studies on one-tier systems. Our findings have implications for both users and public policy and suggest that current European corporate governance regulations could help to increase the decision usefulness of CSR reporting.