Previous research suggests that a couple's ability to balance adverse interactions with positivity is a better predictor of relationship outcomes than negativity per se. The purpose of this study was to extend the findings on couples to parents by examining the positive-to-negative ratio in parental interaction as a predictor of child adjustment. Three hundred seventy-five parents completed questionnaires on the negative and positive interactions in their intimate relationship and their child's functioning online. Different interparental positive–negative ratios were identified by latent class analysis and then linked to children's adjustment. Children whose parents were characterized by more negativity relative to positivity scored higher in externalizing problems compared to children whose parents' negativity was outbalanced by positive interactions. Girls with parents yielding the highest positive–negative ratios were reported to show most prosocial behavior. The findings suggest that parental positivity should be expressed at least twice as much as parental negativity for the sake of children's well-being.