BACKGROUND: Internet-based ACT (Acceptance and commitment therapy) treatment may improve accessibility and reduce stigma related to seeking health care, but there are a lack of studies investigating internet-based treatment using ACT principles for women with vulvodynia. AIM: The aim of this study was to investigate the effects of an internet-based treatment of pain during intercourse for women with provoked vulvodynia compared with no intervention during the waiting period before clinical treatment. METHODS: A multicenter randomized controlled trial was conducted during 2016 to 2020, in which 99 participants were included. Participants were randomized to either a 6 week guided internet-based treatment using ACT principles or usual care. Data were collected at baseline, 6 weeks after baseline, and approximately 10 months after baseline. OUTCOMES: Pain-related (pain during intercourse, tampon test, impact of pain on sexual function) and pain behavior-related outcomes (attempts at intercourse, sexual activities besides intercourse, willingness to perform the tampon test, chronic pain acceptance questionnaire) were used as outcomes. RESULTS: Treatment was efficacious in what concerns pain during intercourse and pain acceptance. Less pain during intercourse among women in the intervention group was observed at both post-treatment (primary endpoint, P = .01, Cohen's d = 1.4, 95% CI = 0.33, 2.4), and follow-up (P = .04). Absolut mean difference between groups for pain during intercourse at post-treatment was -2.84, (95 % CI = -4.91, -0.78), and -1.58 at follow-up, (95 % CI = -3.17, 0.02), where the intervention group rated less pain than controls. No differences between groups over time were found for tampon test measures or impact of pain on sexual function. There was a significant difference between groups at all timepoints indicating fewer attempts at intercourse among participants in the intervention group. At post-treatment, women who underwent internet-based treatment reported higher pain acceptance and a rise in activity engagement compared with the control group. CLINICAL IMPLICATIONS: There is an indication that internet-based treatment could be incorporated into clinical practice as a complement to clinical treatment. STRENGTHS & LIMITATIONS: Study strengths included using several forms of recruitment and an intervention built by different professions with long experience of treating patients with vulvodynia. High dropout rate was a limitation of this study. CONCLUSION: Internet-based treatment may have an impact on pain during intercourse and positive effects on pain acceptance. However, conclusions must be drawn with caution due to the small sample size. Engström AH, Bohm-Starke N, Kullinger M, et al. Internet-based Treatment for Vulvodynia (EMBLA) - A Randomized Controlled Study. J Sex Med 2022;19:319-330.