Cohabitation is a family structure experienced by many Black children; yet, we have limited understanding of how personal and interpersonal processes operate within these families to influence the parenting provided to these children. Informed by both family systems theory and the spillover hypothesis and using a model to account for the interdependence of the mother and her partner, the current study sought to understand the direct and indirect associations among parental mindfulness, the mother–partner relationship quality, and firm parenting practices in a sample of 121 Black cohabiting low-income stepfamilies. Assessment consisted of standardized measurements of maternal and male cohabiting partner reports on mindfulness (i.e., acting with awareness) and relationship quality (i.e., relationship satisfaction, ability to resolve conflict, and coparenting conflict) as well as adolescent report on parenting (i.e., parent's firm control). Mindfulness was directly related to each individual's own perceptions of relationship quality, and some support emerged for a cross-informant link (e.g., mother's mindfulness related to partner report of relationship quality). Furthermore, maternal perceptions of relationship quality, as well as mindfulness operating through relationship quality, were related to youth reports of maternal firm parenting. The results suggest that both mindfulness and the relationship quality of adults are variables deserving attention when studying the parenting received by children in cohabiting stepfamilies. Clinical implications of the findings are considered.