The present study focused on intimacy processes in the relationships of men diagnosed with localized prostate cancer and their partners. Using the actor–partner interdependence model (APIM), we examined the interpersonal process model of intimacy, which proposes associations between self- and perceived partner disclosure about cancer and perceived partner responsiveness as predictors of global relationship intimacy. The study’s outcomes were patients’ and spouses’ ratings of global relationship intimacy. Both actor (my disclosure predicts my intimacy) and partner (my partner’s disclosure predicts my intimacy) effects were examined, as well as possible moderating effects for cancer-related concerns. Two hundred and nine couples in which one or both partners reported elevated cancer-specific distress completed measures of self- and perceived partner disclosure and perceived partner responsiveness regarding discussions about prostate cancer, global relational intimacy, and cancer-related concerns. Results were consistent with the interpersonal process model of intimacy in that perceived responsiveness mediated the association between self- and perceived partner disclosure about cancer and global relational intimacy for both patients and spouses. Results also indicated moderation of the links between disclosure and relational intimacy by level of patient cancer-related concerns such that the links were stronger when concerns were higher. Finally, there was also evidence of moderated mediation such that indirect effects of disclosure on relational intimacy via perceived partner responsiveness were stronger when concerns were higher. Interventions for distressed couples coping with prostate cancer would benefit from focusing on facilitating disclosure and responsiveness, particularly among distressed couples who report cancer concerns.