We test the conjecture that sustainable investing (SI) is driven by altruistic motives by examining the responses of charitable giving and SI flows to exogenous shocks to altruism. We find that while philanthropy responds strongly and significantly, SI flows do not. In addition, two further types of shocks to the reputation and tax shield benefits of philanthropy do not result in an increase in SI either. Our results contribute to understanding the channels behind SI and suggest that altruism is not as an important determinant as previously suggested.