The aim of this study was to test a specific model according to which representations of sexuality (sexual motivation, sexual satisfaction, sexual anxiety, and fear of sex) act as mediators between attachment tendencies and sexual activities (frequency of dyadic and solitary sexual activity and frequency of sexual desire). A community sample of men and women (N = 490; 25–45 years) engaged in an ongoing couple relationship completed questionnaires related to the study variables. After age, duration of relationship, and marital satisfaction were controlled for, the main results showed that (a) in women, higher attachment anxiety was predictive of a higher frequency of dyadic sex and desire for sex; avoidance was predictive of a lower sexual desire; (b) in men, attachment avoidance was predictive of a lower frequency of dyadic sex and desire for sex and of a higher frequency of solitary activity; and (c) most of these effects were indirect and mediated through representations; the paths linking avoidance to sexual activities went mainly through lower positive representations in both women and men (sexual motivation and satisfaction), whereas the paths for anxiety went through a higher negative representation in men (sexual anxiety) and through a higher positive representation in women (sexual motivation). These results were consistent with the deactivation and hyperactivation strategies described for avoidant and anxious tendencies, respectively. However, several suppressor effects were observed, highlighting complex mediational paths. Finally, structural invariance showed that the links between attachment and sexual activities were mediated by representations for both women and men.