Objectives: Sleep problems are highly prevalent among college students and are linked to a multitude of detrimental consequences, among which are heightened perceived stress and symptoms of depression. The present study investigated the effect of poor sleep quality on the immune function of college students. A serial mediation model was developed to test the prediction that perceived stress and depression sequentially mediate the relationship between poor sleep quality and reduced immune function among college students. Participants: 137 undergraduates were recruited from a large Midwestern university (103[subscript Females], 34[subscript Males]; M[subscript age] = 19.47, S[subscript Dage] = ± 1.54). Methods: Cross-sectional based online survey administered in Spring 2021. Results: Analyses revealed a significant total effect of sleep quality on immune function. Perceived stress and depression symptoms serially mediated the relationship between sleep quality and immune function. Conclusions: Results underscore the importance of college students' sleep in relation to their mental health and subsequent immune function.