Romantic relationships help people meet needs for connection and emotional and sexual fulfillment. In the current research, we investigate an unexplored response to feeling sexually and relationally unfulfilled: reflecting on positive sexual experiences with past partners (or sexual nostalgia). Across three studies, people low in attachment avoidance (i.e., comfortable with closeness) who were (a) single or (b) sexually or relationally dissatisfied reported greater sexual nostalgia, whereas people high in attachment avoidance (i.e., value autonomy) did not calibrate their feelings of sexual nostalgia based on their current relationship status or satisfaction. Sexual fantasies about past partners (i.e., sexual nostalgia) were distinct from other types of sexual fantasies (Study 1) and the effects could not be attributed to general nostalgia (Study 2) or sexual desire (Study 3). Chronic sexual nostalgia detracted from satisfaction over time. The findings have implications for theories of nostalgia and attachment and for managing unfulfilled needs in relationships.