Previous research has established that individuals from a lower social class report lower relationship quality. However, to date, no studies have examined interdependence processes within the relationship as a mechanism underlying this association. The present research investigates the role of planned tangible investments as a mediator between social class and relationship quality. Across two studies, we test this hypothesis correlationally (Study 1) and experimentally (Study 2). As predicted, lower-class individuals reported fewer planned tangible investments, which in turn were associated with lower relationship satisfaction and commitment (Studies 1 and 2), as well as overall satisfaction with life (Study 2). Together, these studies suggest the importance of perceived ability to make future plans for individual and relationship well-being. This research has implications for understanding relationship quality and mental health among lower-class populations, and the findings are discussed in relation to the growing literature on social class and romantic relationships.