The aim of the current meta-analysis was to aggregate concurrent and longitudinal empirical research on associations between the interparental relationship and both children's maladjustment (i.e., externalizing and internalizing symptoms) and children's responses to interparental conflict (i.e., emotional, behavioral, cognitive, and physiological). Based on major theoretical frameworks, we distinguished between six dimensions of the interparental relationship: relationship quality, conflict frequency, hostile, disengaged, and unconstructive forms of conflict, and child-related conflict. A final selection of 169 studies for child maladjustment and 61 studies for child responses to conflict were included. The findings revealed by the expansive and fine-grained approach of this meta-analysis support and challenge theoretical hypotheses about the relative predictive value of dimensions of the interparental relationship for children's functioning. Although hostility was specifically more strongly associated with children's externalizing behavior and emotional responses to conflict, disengaged and unconstructive conflict behavior posed similar risks for the other domains of child functioning. In addition, relationship quality, conflict frequency, and child-related conflict warrant more attention in theoretical frameworks, as these dimensions posed similar risks to child functioning as the different forms of conflict. Moreover, most associations between the interparental relationship and child functioning endured over time. Also, developmental and gender differences appeared to depend on the specific forms of interparental conflict and the domain of child functioning. In sum, the results support the growing consensus that prevention and intervention programs aimed at children's mental health could benefit from an alternative or additional focus on the interparental relationship. Public Significance Statement This meta-analysis pooled findings from previous research on associations between different aspects of the interparental relationship and children's maladjustment (i.e., externalizing and internalizing problems) and responses to interparental conflict (i.e., emotional, behavioral, and physiological reactivity, and cognitive appraisals of the interparental subsystem). The findings highlight the importance of both the general quality of the relationship between parents as well as five aspects of interparental conflicts (i.e., conflict frequency, the level of hostile, disengaged and unconstructive conflict behavior, and the amount of child-related conflicts) as robust predictors of children's maladjustment, concurrently and over time. Moreover, the findings confirm that children's emotional and behavioral reactivity to interparental conflicts, and their cognitive appraisals of the interparental subsystem, are fruitful directions for understanding why interparental conflict leads to maladjustment in children.