Objective: Previous longitudinal studies have demonstrated prospective relationships between maternal sleep quality and subsequent psychological distress in the postpartum period. Despite evidence for prospective relationships between mood and subsequent sleep quality in adult populations, this direction has not been examined in postpartum women. We aimed to test prospective relationships between sleep quality and subsequent psychological distress, as well as the plausible reverse possibility, in a sample of Black American postpartum mothers (n = 146).Participants: Mothers were recruited prenatally from two hospitals in a Southeastern city of the United States. Eligible and interested mothers enrolled in a follow-up study on infant development. Data from the current study were obtained during the follow-up study.Method: Mothers reported on their psychological distress (i.e., anxiety, depression, stress) and sleep quality at 3- and 6-months postpartum. We performed hierarchical linear regressions to explore whether 1) maternal sleep quality at 3-months postpartum would predict maternal psychological distress at 6-months postpartum, after adjustment for mothers' earlier psychological distress, and 2) whether psychological distress at 3-months postpartum would predict maternal sleep quality at 6-months postpartum, after adjustment for mothers' earlier sleep quality.Results: Maternal sleep quality at 3-months postpartum was not a significant predictor of psychological distress at 6-months postpartum. However, maternal psychological distress at 3-months postpartum was a significant predictor of sleep quality at 6-months postpartum.Conclusions: Mothers' psychological distress earlier in the postpartum was a significant predictor of their later sleep quality. Replication is needed in large, prospective studies, with results stratified by race/ethnicity.