People tend to overestimate emotional responses to future events. This study examined whether such affective forecasting errors occur for feelings of regret, as measured by self-report and subsequent decision-making. Some participants played a pricing game and lost by a narrow or wide margin, while others were asked to imagine losing by such margins. Participants who experienced a narrow loss reported more regret than those who imagined a narrow loss. Furthermore, those experiencing a narrow loss behaved more cautiously in a subsequent gambling task. Thus, the study provides self-report and behavioral evidence for a reversal of the affective forecasting phenomenon for feelings of regret.