Objective: We investigate whether obesity is associated with sexual activity, sexual frequency, and the range of sexual behaviors in heterosexual older couples. We assess to what extent associations between obesity and sexuality are explained by physical, psychological, and sexual health, and by relationship quality. Method: We use data from 1,698 older adults in 849 partnered dyads in the 2010-2011 wave of the National Social Life, Health, and Aging Project and conduct couple-level analysis featuring women’s and men’s characteristics. Results: Women’s obesity—particularly at severe levels—is negatively associated with coupled sexual activity, and that the association is not mediated by hypothesized mediators. Men’s obesity did not have any association with sexual activity. There was no significant difference between overweight and normal weight adults across all three sexuality measures. Discussion: The growing number of older adults with high levels of body mass index, particularly women, may face certain difficulties in maintaining active sexual lives.