AbstractResearch clearly demonstrates that conflictual interparental relationship dynamics can create a family context that contributes to child emotional insecurity and psychopathology. Significantly less research has examined familial factors that contribute to maladaptive conflict between parents. Scholars have alluded to the disruptive impacts of parenting a child with certain temperamental characteristics (e.g., negative emotionality). Yet, there is a lack of empirical research examining if and how child temperament contributes to later interparental conflict. Using an established multi‐informant, multi‐method sample of 150 families first assessed during pregnancy, and again when the child was 1, 2, and 3.5 years of age, the present study aimed to test an integrated conceptual model examining whether infants' negative emotionality assessed at age 1 predicts interparental conflict at age 3.5, as mediated through destructive coparenting dynamics in toddlerhood, and identifying prenatal protective factors mitigating this maladaptive pathway. Findings suggest that greater infant negative emotionality predicts worse interparental conflict management during preschool age by undermining the mother's (but not the father's) report of coparenting relationship quality during toddlerhood. However, these results were significant only to the extent that parents were lacking certain prenatal regulatory resources (i.e., low paternal self‐compassion; less secure relationship between parents). Importantly, results point to the need for intervention and prevention efforts during pregnancy that might disrupt the deleterious impacts of parenting a child who is more reactive and prone to expressing negative emotions.