A large body of evidence demonstrates that childhood interpersonal trauma is associated with poorer parental and couple outcomes following the birth of a new child. As a unique component of couple functioning, parenting alliance is key during this transition period and is associated with long-term parental and child well-being. However, parenting alliance remains understudied in relation to childhood trauma, and little is known regarding the underlying mechanisms of this relationship among couples. Given its documented role in the intimate relationships of childhood interpersonal trauma-exposed individuals, dispositional mindfulness could be considered as a potential explanatory mechanism. Using a dyadic approach, this study examined the role of dispositional mindfulness, and its different facets, in the association between cumulative childhood interpersonal trauma (CCIT) and parenting alliance. A randomly selected community sample of 421 parental couples with infants completed online questionnaires. For both mothers and fathers, CCIT was associated with a more negative perception of parenting alliance through lower dispositional mindfulness, specifically through lower scores on the nonjudgment and describing facets. Moreover, results revealed dyadic indirect effects between parents' CCIT and their partner's parenting alliance through both partners' dispositional mindfulness. This study provides insight on how parents of an infant may influence each other's perceived parenting alliance through their dispositional mindfulness. Results also highlight mindfulness as a relevant mechanism for CCIT survivors who struggle to establish or maintain a positive parenting alliance, as well as the need to involve both parents in research and intervention. (PsycInfo Database Record (c) 2024 APA, all rights reserved).