The recent NCCN Guidelines for Survivorship recommend systematic evaluation and multidisciplinary treatment of cancer-related sexual dysfunctions. However, most oncology professionals fail to routinely assess sexual problems and lack expertise to treat them. An Internet-based intervention was designed to educate female patients and their partners about cancer-related sexual problems, describe medical treatment options and how to find expert care, and provide self-help strategies. A randomized trial assessed efficacy of the intervention when used as self-help versus the same Web access and 3 supplemental counseling sessions. Survivors of localized breast or gynecologic cancers completed online questionnaires at baseline, posttreatment, and 3- and 6-month follow-up, including the Female Sexual Function Index (FSFI), the Menopausal Sexual Interest Questionnaire (MSIQ), the Brief Symptom Inventory-18 (BSI-18) to assess emotional distress, and the Quality of Life in Adult Cancer Survivors (QLACS) scale. Program evaluation ratings were completed posttreatment. Fifty-eight women completed baseline questionnaires (mean age, 53 ± 9 years). Drop-out rates were 22% during treatment and 34% at 6-month follow-up. Linear mixed models for each outcome across time showed improvement in total scores on the FSFI, MSIQ, and QLACS (P<.001) and BSI-18 (P=.001). The counseled group improved significantly more on sexuality measures, but changes in emotional distress and quality of life did not differ between groups. Program content and ease of use were rated positively. Research is needed on how best to integrate this intervention into routine clinical practice, and particularly how to improve uptake and adherence.