Third-party punishment has recently received attention as an explanation for human altruism. Feelings of anger in response to norm violations are assumed to motivate third-party sanctions, yet there is only sparse and indirect support for this idea. We investigated the impact of both anger and guilt feelings on third-party sanctions. In two studies both emotions were independently manipulated. Results show that anger and guilt independently constitute sufficient but not necessary causes of punishment. Low levels of punishment are observed only when neither emotion is elicited. We discuss the implications of these findings for the functions of altruistic sanctions.