Quality of marital relationships is consistently linked to personal well-being. However, almost all of the studies linking marital processes to well-being have been conducted in Western (particularly North American) countries. Growing evidence shows that perceived partner responsiveness is a central relationship process predicting well-being in Western contexts but little is known about whether this association generalizes to other countries. The present work investigated whether the predictive role of perceived partner responsiveness in well-being differs across the United States and Japan—2 contexts with contrasting views on how the self is conceptualized in relation to the social group. A large life span sample of married or long-term cohabiting adults (n = 3,079, age range = 33–83 in the United States and n = 861, age range = 30–79 in Japan) completed measures of perceived partner responsiveness, hedonic and eudaimonic well-being, and demographic (age, gender, education) and personality (extraversion and neuroticism) covariates known to predict well-being. Perceived partner responsiveness positively predicted hedonic and eudaimonic well-being both in the U.S. and in Japan. However, perceived partner responsiveness more strongly predicted both types of well-being in the United States as compared with Japan. The difference in slopes across the 2 countries was greater for eudaimonic as compared with hedonic well-being. The interaction between perceived partner responsiveness and country held even after controlling for demographic factors and personality traits. By showing that the role of perceived partner responsiveness in well-being may be influenced by cultural context, our findings contribute to achieving a more nuanced picture of the role of relationships in personal well-being.