The aim of this investigation was to evaluate Internet-based cognitive-behavioral therapy for tinnitus in a nonrandomized clinical effectiveness study with a sample of consecutive patients referred for psychological treatment (N = 77). Results were calculated at a group level on an intention-to-treat basis and showed significant reductions of distress on the Tinnitus Reaction Questionnaire (P. H. Wilson, J. Henry, M. Bowen, & G. Haralambous, 1991), the Hospital Anxiety and Depression Scale (A. S. Zigmond & R. P. Snaith, 1983), and on the Insomnia Severity Index (C. H. Bastien, A. Vallières, & C. M. Morin, 2001). A 3-month follow-up showed that patients remained improved. The dropout rate was 30%. Treatment compliance, external referral to the treatment, and number of earlier treatments for tinnitus were associated with positive outcome. The number of e-mails between therapist and patient concerning treatment problems was associated with worse outcome. Internet-based cognitive-behavioral therapy holds some promise as a treatment modality for tinnitus. Future research should focus on further controlled evaluations of the treatment technique and evaluate the cost-effectiveness compared to other forms of tinnitus treatments.