This study examined associations among marital quality, coparenting, and parenting self-efficacy in parents of young children. Of special interest were possible spillover and stress-buffering effects of the marital and coparenting relationships. The authors sampled 175 married and cohabiting couples. Participants were recruited via an online marketing company and completed surveys on the project’s website. Maintenance strategies were associated with higher parenting self-efficacy for mothers and fathers, and for mothers, their spouse’s reports of his own maintenance behaviors were associated with increased parenting self-efficacy. Undermining coparenting predicted lower parenting self-efficacy for mothers and fathers. There was support for the spillover and stress-buffering hypotheses as evidenced by significant interactions between marital qualities and coparenting predicting to parenting self-efficacy. Findings support a connection between marital and coparenting subsystems; whereby, positivity in one of these relationships can interact to buffer the effects of negativity in the other to maintain or increase parenting self-efficacy.