Several prominent models of relationship satisfaction and sexual satisfaction imply directional relationships between these constructs (e.g., attachment theory, social exchange models of relationship satisfaction, the interpersonal exchange model of sexual satisfaction). Previous research has demonstrated that sexual satisfaction and relationship satisfaction are distinct but correlated constructs, but relatively few studies have examined how they are related over time. Thus, the purpose of this study was to examine this association. A sample of heterosexual couples (N = 113) completed a longitudinal study spanning 2 years. At Times 1 and 2 they completed measures of relationship satisfaction and sexual satisfaction. Data were analyzed according to the principles of the actor–partner interdependence model using structural equation modeling. Significant actor effects were detected such that, for both men and women, one’s own earlier sexual satisfaction predicted one’s later relationship satisfaction. In contrast, one’s own earlier relationship satisfaction did not significantly predict one’s subsequent sexual satisfaction. Sexual satisfaction was a stronger predictor of subsequent relationship satisfaction for men than women. There were no significant partner effects. These results contribute to our theoretical understanding of sexuality and sexual satisfaction in the context of long-term relationships by providing support for theories that conceptualize sexual satisfaction as one factor that contributes to relationship satisfaction.