Mechanisms accounting for the effects of mutually responsive orientation (MRO) at 7, 15, and 25 months in 102 mother-child and father-child dyads on child internalization and self-regulation at 52 months were examined. Two mediators at 38 months were tested: parental power assertion and child self-representation. For mother-child relationships, the causal pathway involving power assertion was supported for both outcomes. Diminished power assertion fully mediated beneficial effect of mother-child MRO on internalization and partially mediated its effect on self-regulation. For father-child relationships, MRO predicted self-regulation, but the mediational paths were unsupported. Paternal power assertion correlated negatively with both outcomes but was not a mediator. Although MRO with both parents correlated with child self-representation, and it correlated with self-regulation, this mediational path was unsupported.