Cause marketing (CM) is commonly implemented to pursue profit growth or/and achieve corporate social responsibility (CSR). In online retailing, to facilitate CM for the products, e-retailers are increasingly implementing CM programs for the firms that sell products directly to consumers, i.e., suppliers under agency selling mode or themselves under reselling mode. Motivated by this, we examine when and whether an e-retailer should implement its CM program, and how it influences the supply chain members. Our results show that while the CM program can benefit both the supply chain members by expanding the demand, it can also reduce their performance when it induces the selling mode to be changed.