Research has evidenced support for the spillover model, which asserts that parents' marital functioning influences their parenting and coparenting behavior in dyadic (mother-child and father-child) and triadic (mother-father-child) family contexts. However, few studies have simultaneously investigated the spillover model in both parenting and coparenting systems, preventing examination of whether spillover impacts both systems equally or differentially. Further, little research has examined whether quality of the marital system influences children's behavior toward their parents, as well as their parents' behavior, in dyadic interactions. We examined the spillover model using observational measures of parent and child behavior in parent–child dyadic interactions as well as coparenting in triadic interactions. We also explored parent and child gender differences in spillover effects. Participants were families with children aged 3 to 6 years (n = 149). Findings indicated that spillover occurs to multiple family systems, but the effects varied according to whose behavior (mother, father, child) was explored. In families of boys and girls, the marital system influenced warmth in triadic interactions, as well as fathers' responsiveness and children's responsiveness to mothers in dyadic interactions. Spillover effects were largely equivalent for girls and boys, but spillover to coparenting hostility in triadic interactions was limited to families raising girls. Parent gender also moderated associations between marital functioning and parent–child interactions: Spillover was significantly stronger for fathers' responsiveness (vs. mothers' responsiveness) and child responsiveness to mothers (vs. child responsiveness to fathers).