Provoked vestibulodynia (PVD) is a chronic vulvovaginal pain condition affecting 8%-10% of women and is associated with negative sexual sequalae. Our randomized clinical trial comparing cognitive-behavioral couple therapy (CBCT) to a medical intervention (lidocaine) found that both treatments improved affected women's pain and both affected women's and partners' sexual outcomes, with CBCT demonstrating more benefits (Bergeron et al., 2021). The goal of this study was to examine two putative mediators of CBCT's treatment effects: collaborative and negative sexual communication patterns (SCPs). Women with PVD and their partners were randomly assigned to 12 weeks of CBCT (N = 53) or lidocaine (N = 55). Outcome measures (sexual satisfaction, function, and distress) were collected at pre-treatment, post-treatment, and 6-month follow-up, and in-treatment measures of the mediators were taken at Weeks 1, 4, 8, and 12 of treatment. Results showed that affected women's reports of improving collaborative communication mediated the effect of CBCT, but not lidocaine, on post-treatment sexual satisfaction (women with PVD and partners), sexual function (women with PVD), and sexual distress (women with PVD). For partners, collaborative communication improved equally in both treatments. Given that there were no differences in negative SCPs between the CBCT and lidocaine conditions, it was not possible to examine negative communication as a potential mediator. From the perspective of women with PVD, CBCT helped couples communicate about their sexual problems in more collaborative ways, which was in turn beneficial for improving the sexual well-being of both members of the couple. (PsycInfo Database Record (c) 2022 APA, all rights reserved).