Building on empirical documentation of children’s involvement in interparental conflicts as a weak predictor of psychopathology, we tested the hypothesis that involvement in conflict more consistently serves as a moderator of associations between children’s emotional reactivity to interparental conflict and their psychological problems. In Study 1, 263 early adolescents (M age = 12.62 years), mothers, and fathers completed surveys of family and child functioning at 2 measurement occasions spaced 2 years apart. In Study 2, 243 preschool children (M age = 4.60 years) participated in a multimethod (i.e., observations, structured interview, surveys) measurement battery to assess family functioning, children’s reactivity to interparental conflict, and their psychological adjustment. Across both studies, latent difference score analyses revealed that involvement moderated associations between emotional reactivity and children’s increases in psychological (i.e., internalizing and externalizing) problems. Children’s emotional reactivity to interparental conflict was a significantly stronger predictor of their psychological maladjustment when they were highly involved in the conflicts. In addition, the developmental benefits and costs of involvement varied as a function of emotional reactivity. Involvement in interparental conflict predicted increases in psychological problems for children experiencing high emotional reactivity and decreases in psychological problems when they exhibited low emotional reactivity. We interpret the results in the context of the new formulation of emotional security theory (e.g., Davies & Martin, 2013) and family systems models of children’s parentification (e.g., Byng-Hall, 2002).