Objectives. Previous studies have observed a rebound of marital quality in later adulthood. This study tested whether partner discrepancy was a mediator of the age differences in marital quality. Method. The present study assessed partner discrepancies and marital quality in 56 couples, 20–79 years old. Two levels of partner standards (ideal and expected standards) and 2 domains of partner characteristics (personality and support) were examined. Results. Husbands’ partner discrepancies, but not wives’, were found to mediate the curvilinear age differences in martial quality. Discussion. Consistent with the life-span theory of control, the results suggest that adjusting cognition about the partner is essential to the typically higher marital quality in later adulthood. The results also suggest that the level of comparison standards and the specific domain of partner characteristics should be considered in future studies.