Background: This study examined the bidirectional nature of mother-infant positive and negative emotional displays during social interactions across multiple tasks among postpartum women accounting for childhood maltreatment severity. Additionally, effects of maternal postpartum psychopathology on maternal affect and effects of task and emotional valence on dyadic emotional displays were evaluated. Sampling and Methods: A total of 192 mother-infant dyads (51% male infants) were videotaped during free play and the Still-Face paradigm at 6 months postpartum. Mothers reported on trauma history and postpartum depression and posttraumatic stress disorder (PTSD) symptoms. Reliable, masked coders scored maternal and infant positive and negative affect from the videotaped interactions. Results: Three path models evaluated whether dyadic affective displays were primarily mother driven, infant driven, or bidirectional in nature, adjusting for mothers' maltreatment severity and postpartum psychopathology. The bidirectional model had the best fit. Child maltreatment severity predicted depression and PTSD symptoms, and maternal symptoms predicted affective displays (both positive and negative), but the pattern differed for depressive symptoms compared to PTSD symptoms. Emotional valence and task altered the nature of bidirectional affective displays. Conclusions: The results add to our understanding of dyadic affective exchanges in the context of maternal risk (childhood maltreatment history, postpartum symptoms of depression and PTSD). Findings highlight postpartum depression symptoms as one mechanism of risk transmission from maternal maltreatment history to impacted parent-child interactions. Limitations include reliance on self-reported psychological symptoms and that the sample size prohibited testing of moderation analyses. Developmental and clinical implications are discussed.