Cause marketing (CM) is commonly adopted 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. In this context, this paper studies the CM strategies of supply chain members in the presence of private label. We find that under reselling mode, the supply chain members will always conduct CM for their own products, while under agency selling mode, the supply chain members conduct CM for their own products only when the retailer makes the first move. Interestingly, we find that the e-retailer can seize more profit through the competition between its private label and the national brand, which renders the supplier to not benefit from cause marketing or even get hurt.