Objective Cognitive behavioural treatment (CBT) for the reduction of tinnitus complaints have been shown to be effective; however the specific mechanisms of change are yet to be unveiled. Reductions in tinnitus-related fear have been indicated to be an important factor in alleviating tinnitus suffering. The role of tinnitus-related fear is proposed as an important mediator explaining the cognitive behavioural treatment effects on tinnitus severity, tinnitus-related impairment and general quality of life of tinnitus patients. Methods: A two-group, single-centre RCT was carried out with adult tinnitus patients (n=492), with 3 follow-up assessments up to 12 months after randomization. Patients were randomly assigned to Usual Care (UC) or Specialised cognitive behavioral stepped Care (SC). A repeated-measures design, with group as a between subjects factor, and time as the within-subject factor, was used in an intention-to-treat analysis. Mixed regressions for assessing mediation effects were performed with general health, tinnitus distress, tinnitus related impairment as the dependent variables and tinnitus related fear as the mediator variable. Results: Tinnitus-related fear appears to mediate part of the treatment benefits of specialized care, as compared to usual care, with respect to increased quality of life ratings, and decreased tinnitus severity and tinnitus related impairments. Conclusions: The effectiveness of cognitive behavioural treatment approaches might be partly explained by significant reductions in tinnitus-related fear. These results are relevant in that currently, though CBT approaches in tinnitus management have been proven to lead to decreased suffering of tinnitus patients, the psychological mechanisms causing these benefits are still to be discovered.