We addressed the relation between sleep quality and aspects of the self. In particular, we conducted three studies using cross-sectional and longitudinal, as well as subjective and behavioral, methods to examine the link between sleep quality and four self-aspects: self-esteem, self-compassion, self-control, self-continuity. Past month sleep quality positively related to trait levels of all four self-aspects (Studies 1-2). Daily reports of sleep quality were positively associated with state levels of all four self-aspects across 14 days (Study 2) and 7 days (Study 3). Cross-lagged paths revealed that subjective sleep quality predicted the four self-aspects but not vice-versa (Studies 2-3). A behavioral index of sleep quality (i.e. sleep efficiency) did not predict any self-aspect, but self-compassion and self-continuity predicted sleep efficiency (Study 3). The findings clarify the association between sleep quality and the self, providing explanations for the psychological benefits of a good night's sleep.