OBJECTIVE:This set of studies examines the bidirectional links between social rejection and poor sleep, a ubiquitous and increasingly problematic health behavior. METHODS:In study 1, a multiday field experiment, 43 participants completed a neutral task just before sleep on night 1 and a social rejection task on night 2. Objective and subjective sleep, postrejection affect, and physiological responses were measured. In study 2, 338 participants reported typical sleep quality before coming to the laboratory where they received social rejection or social acceptance feedback from a stranger. Physiological and affective responses were measured throughout the session. RESULTS:In study 1, after social rejection, participants took longer going to bed (M [SD] = 38.06 [48.56] versus 11.18 [15.52], t(42) = 3.86, p < .001) and had shorter sleep durations (6:46 [1:27] versus 7:19 [1:38], t(41) = 2.92, p = .006) compared with the baseline night. Trait rumination moderated these effects, with high ruminators taking the longest to go to bed postrejection (t(38) = 2.90, p = .006). In both studies, there was (inconsistent) evidence that sleep influences reactions to rejection: some sleep measures predicted physiological reactivity during the rejection task in study 1 and greater negative affect after social rejection in study 2. CONCLUSIONS:These studies provide evidence that social rejection may affect sleep outcomes, particularly for trait ruminators, and poor sleep in turn may exacerbate affective responses to social rejection. Given the mixed findings, small sample size, and no active control condition, more work is needed to confirm and build on these findings.