Marital processes in early marriage are important for understanding couples' future marital quality. Spouses' attributions about a partner's behavior have been linked to marital quality, yet the mechanisms underlying this association remain largely unknown. When we used couple data from the Family Transitions Project (N = 280 couples) across the first 4 years of marriage, results from actor-partner interdependence modeling demonstrated that early marriage responsibility attributions were associated with marital quality 4 years later after controlling for initial marital quality. Further, couples' warm and hostile behavior 2 years into the marriage mediated the attribution-marital quality association. The results suggest that interventions designed to facilitate change in romantic relationships may benefit from addressing attributions for the partner's behavior, in addition to changing behaviors, as part of a dyadic process unfolding across time.