<p>Corporate social responsibility (CSR) has received significant attention in recent years. Nevertheless, more is needed to know about the appropriate CSR policy within a supply-chain. This study examines whether the manufacturer or the retailer should undertake CSR in a bilateral monopoly supply chain. We focus on a scenario in which a manufacturer distributes a featured product to end consumers through a retailer, and they implement a revenue-sharing contract. The manufacturer decides the CSR investment and wholesale price, while the retailer determines the retail price and revenue sharing proportion. Based on a differential game framework, our analysis considers two cases: the manufacturer undertaking CSR and the retailer undertaking CSR; the supply chain members who undertake CSR consider both their monetary profit and consumer surplus. Our results show that steady-state outcomes are the same when the manufacturer and retailer have the equal levels of caring about consumers. The manufacturer’s monetary profit first increases and then decreases as its level of caring about consumers increases under a revenue-sharing contract. In contrast, the retailer’s monetary profit first increases and then decreases as its level of caring about consumers increases under a wholesale contract. Our study highlights the importance of the interactions between CSR and contract mechanisms in supply chain management.</p>