["Japanese Psychological Research, EarlyView. ", "\nAbstract\nMost research on post‐purchase regret has relied mostly on data from choice tasks rather than rejection tasks. The aim of the present work was therefore to test whether post‐purchase regret is alleviated when decision tasks are performed in rejection‐based rather than choice‐based formats. It reports on three studies, each of which was conducted to analyze how a choice task and rejection task might lead to divergent post‐purchase regret outcomes. Collectively, the results of these studies established that the participants felt less regret when engaging in a rejection task than in a choice task, and that the effect of choice/rejection difference on post‐purchase regret was mediated by the level of process fluency. In other words, the effect of the decision task type (choice/rejection) on post‐purchase regret was lesser when process fluency was low than when it was high. The findings of this research can help marketers to reduce consumers' regret by controlling purchase‐decision task types.\n"]