Previous research on the role of negative emotions in social bargaining games has focused primarily on social emotions such as anger and guilt. In this article, we provide a test for behavioural differences between two prototypical decision-related negative emotions—regret and disappointment—in one-shot social dilemma games. Three experiments with two different emotion-induction procedures (autobiographical recall and imagined scenarios) and two different games (the ultimatum game and the 10-coin give-some game) revealed that regret increased prosocial behaviour, whereas disappointment decreased prosocial behaviour. These (...) results extend previous findings concerning differences between regret and disappointment to interdependent (social) situations. (shrink)