Previous research has indicated that men generally rate slimmer women as more sexually attractive, consistent with the increased morbidity risks associated with even mild abdominal adiposity. To assess the association of women’s waist size with a more tangible measure of perceived sexual attractiveness (as well as reward value for both sexes), we examined the association of women’s age and waist circumference with an index of men’s erectile function (IIEF-5 scores), frequency of penile-vaginal intercourse (PVI), and sexual satisfaction in a representative sample of Czechs (699 men and 715 women) aged 35–65 years. Multivariate analyses indicated that better erectile function scores were independently associated with younger age of self and partner and women’s slimmer waist. PVI frequency was independently associated with women’s younger age and women’s slimmer waist. Sexual satisfaction was independently associated with men’s younger age and slimmer waist for both sexes. Better erectile function, greater PVI frequency, and greater sexual satisfaction were associated with women’s slimmer waist, independently of both sexes’ ages. Possible reasons for the waist effects were discussed, including women’s abdominal body fat decreasing their own desire through neurohormonal mechanisms and decreasing their partner’s desire through evolutionarily-related decreased sexual attractiveness.