This study examined the relationship between stress and sleep duration for adolescent females from affluent backgrounds. Participants were 218 students attending two independent single-sex secondary schools. Ordinary Least Squares (OLS) regression models (cross-sectional and longitudinal) were run to examine the association between stress and sleep duration and to determine whether any associations lasted from the beginning to the end of the academic year. In the cross-sectional models, the relationship between perceived stress and sleep duration was reciprocal and negative. Findings from the longitudinal analyses suggested that perceived stress had lingering negative effects on sleep. Implications for future research and practice are discussed.