As a development-enhancing or a risk-promoting environment, coparenting may shape the association between maternal prenatal depressive symptoms and infant regulatory capacity. This study aimed to analyze the moderator role of positive and negative coparenting in the association between maternal prenatal depressive symptoms and infant regulatory capacity at 3 months. A sample of 103 primiparous couples (N = 206 parents) was recruited at the 1st trimester of pregnancy. Mothers reported on depressive symptoms at the 1st trimester of pregnancy, and both parents reported on depressive symptoms, coparenting, and infant regulatory capacity at 2 weeks and 3 months postpartum. Higher levels of maternal prenatal depressive symptoms and higher levels of maternal and paternal reports of negative coparenting at 2 weeks postpartum were associated with lower infant regulatory capacity at 3 months. Negative coparenting at 2 weeks postpartum accentuated the association between maternal prenatal depressive symptoms and infant regulatory capacity at 3 months. The results support a view of negative coparenting as a risk-promoting environment that can accentuate the association between maternal prenatal depressive symptoms and infant regulatory capacity. Infants in families with mothers with elevated prenatal depressive symptoms and with high levels of negative coparenting may be at high risk of low regulatory capacity.