The role of autobiographical memory in emotion regulation is deemed as limited to the selective retrieval of positive memories intended as a distraction from unpleasant stimuli. The present experimental study is the first to examine whether negative autobiographical memories serve as a way to boost one’s mood by employing the mechanism of retrospective downward autobiographical comparison between now and then. We hypothesised that this mechanism may operate in response to negative memories, leading to positive mood induction. Ninety-nine students participated in four memory tasks: autobiographical positive, autobiographical negative, vicarious positive, and vicarious negative. Emotional states at pre- and post-tests were assessed using the implicit test differentiating positive (PA) and negative (NA) components of mood. The results replicated previous studies on the mood-repair effect of deliberate positive recall. The most striking finding is that negative autobiographical recall consistently boosted PA and inhibited NA. This result supported the idea of retrospective downward autobiographical comparison as a plausible mechanism behind the efficacy of negative memories in emotion regulation.