Autobiographical memories are hypothesised to serve at least three functions: they direct people’s behaviour, inform their identity, and facilitate social bonding. But most of the research on these three functions has focused on how memories serve them in ways that are adaptive—in fact, we know little about how memories might serve functions in ways that are maladaptive. We also know little about the factors that drive memories to serve functions in adaptive or maladaptive ways. Across four sets of experiments, we1 investigated both the extent to which memories serve maladaptive functions and the factors that drive memories to serve functions in adaptive or maladaptive ways. We found that people’s positive memories are primarily adaptive, whereas their negative memories serve a mix of adaptive and maladaptive functions. In addition, we found that the more a memory is associated with a sense of reliving, the more adaptive it tends to be. Finally, we found evidence that it is not necessary for people to have personally experienced an event, nor for them to believe an event really happened, in order for the memory of that event to serve functions. Considered together, these data highlight the need for researchers to take more nuanced view of the functions of autobiographical memory and demonstrate the importance of measures that separate adaptive and maladaptive functions.