Body satisfaction predicts sexual quality among women and men; however, mechanisms of the association are largely unknown. We hypothesized that sexual anxiety would mediate average associations over 1 year between individuals’ body satisfaction and their own and their partner’s sexual quality, which is comprised of their sexual satisfaction and dissatisfaction, in 123 mixed-sex cohabiting couples. Results of Actor–Partner Interdependence Models extended to Mediation (APIMeM) and tested via multilevel modelling partially supported the hypotheses. Specifically, individuals’ body satisfaction indirectly predicted their own and their partner’s sexual satisfaction through individuals’ sexual anxiety, and indirectly predicted their own, but not their partner’s sexual dissatisfaction through individuals’ sexual anxiety. Thus, when individuals are relatively less satisfied with their bodies, they may experience anxiety during sexual encounters, which then interferes with their own and their partner’s sexual quality.