We document a link between the relational diversity of one’s social portfolio—the richness and evenness of relationship types across one’s social interactions—and well-being. Across four distinct samples, respondents from the United States who completed a preregistered survey ( n = 578), respondents to the American Time Use Survey ( n = 19,197), respondents to the World Health Organization’s Study on Global Aging and Adult Health ( n = 10,447), and users of a French mobile application ( n = 21,644), specification curve analyses show that the positive relationship between social portfolio diversity and well-being is robust across different metrics of well-being, different categorizations of relationship types, and the inclusion of a wide range of covariates. Over and above people’s total amount of social interaction and the diversity of activities they engage in, the relational diversity of their social portfolio is a unique predictor of well-being, both between individuals and within individuals over time.