<p>People often wish they could reverse previous decisions. However, few sequential decision-making tasks used in the literature allow participants to undo their decisions. As a result, it remains an open question when, how, and why people reverse their decisions. We designed a sequential decision-making task in which the participant connected cities on a map using a limited road budget, either without or with the option to undo their decisions. We found that when decisions were reversible, participants spent less time on their first action, progressively improved on their solutions through decision reversals, and ultimately achieved better final performance. Furthermore, decision reversals predominantly corrected errors, and did so with greater precision when errors were larger. Finally, we found evidence that decision reversals were predicted by factors that may be associated with a subjective prior probability of an error. Taken together, our results are consistent with a view in which uncertainty about being on the right track – both retrospective and prospective – drives decision reversals. Our work opens the door to neurocognitive, computational and translational studies of decision reversals.</p>