We show that optimistic beliefs regarding the role of effort in success, while leading to success, diminish the individual’s sympathy toward the unsuccessful. We generate random variation in the degree of optimism about the productivity of effort via an effective educational intervention. We find that treated children, holding significantly more optimistic beliefs, are no less likely than control to give to unlucky recipients, but significantly less likely to give to those who failed at a real effort task despite an opportunity to build skill. The results highlight possible unintended social effects of effort-focused optimism and have implications for political economy.