We consider a supply chain in which a seller produces a finished product and sells it on the marketplace of a retail platform. The seller may invest in Corporate Social Responsibility (CSR) to increase the market demand but has limited capital and no access to bank financing due to low credit rating. To mitigate the seller's capital constraint, the retail platform offers financial loans to the seller choosing among three kinds of loan contracts Credit limit, target rate of return, and interest rate discount based on CSR performance. We adopt a Stackelberg game to investigate the equilibrium decisions under each loan contract. The numerical examples reveal that all three contracts help improve the seller's CSR investment as long as consumer sensitivity towards CSR exists. In addition, the last one leads to the highest profitability of the overall supply chain and each member. © Interconnected Supply Chains in an Era of Innovation - Proceedings of the 8th International Conference on Information Systems, Logistics and Supply Chain, ILS 2020. All rights reserved.