We investigated the association between marital quality and child behavior, assessing mother–child relationship quality as a potential mediator. The sample included 78 mothers with two target children (mean ages = 9.82 and 12.05 years, respectively). Mothers reported on their children’s behavior as well as their marital quality, while each child reported on their relationship with their mother. Confirming our hypothesis, marital quality did relate to child behavior. Contrary to our expectations, the mother–child relationship provided negligible mediation of the link, but did provide significant prediction of child behavior in its own right. Importantly, our findings show differential outcomes for children within the same family, supporting a differentiated child-specific outlook. Further evidence that both marital quality and shared, as well as differential, mother–child relationships link with child behavior is provided here. Consequently, interventions with the aim of decreasing children’s behavioral problems and increasing more positive conduct can usefully include a focus on the nature of the parents’ romantic relationship, alongside parenting.