Introduction Sleep loss is common during the perinatal period; however, few studies have assessed potential consequences of insufficient sleep for postnatal emotional responding, a key contributor to parenting behaviors with implications for parent-infant bonding and mental health. To generate hypotheses for future work assessing perinatal sleep and emotion-related outcomes, this pilot study explored whether prenatal sleep duration predicted postnatal emotional responding in a sample at risk for postpartum depression. Methods Participants were 9 birthing parents with a prior mood disorder who were not in a current episode at enrollment. We estimated sleep with actigraphy collected for one week at 33 weeks’ gestation and at 2 and 6 weeks postpartum. Following each week, participants completed an emotional evaluation task, rating the valence and arousal of standardized images from the International Affective Picture System (IAPS). We tested whether average prenatal (33 weeks) nighttime sleep duration predicted concurrent and future responsiveness to emotional images, quantified by participants’ reaction times and arousal/valence ratings. Results Shorter prenatal sleep duration predicted faster reaction times, both concurrently and at 2 weeks postpartum (ps≤.05), as well as lower arousal ratings for negative images at 2 and 6 weeks postpartum (ps≤.043). Conclusions In this small sample of birthing parents at risk for postpartum depression, shorter prenatal sleep duration predicted faster reactions to emotional stimuli and blunted arousal responses to negative images. Although preliminary, these findings justify further study of the role of prenatal sleep in postpartum emotional responses and how these factors may impact parent-infant outcomes.