Hyperacusis, defined as unusual intolerance to ordinary environmental sounds, is a common problem for which there are no controlled trials on psychological treatment. Given the avoidance strategies present in hyperacusis, and similarities with problems such as tinnitus and chronic pain, cognitive behaviour therapy (CBT) is hypothesized to be helpful for patients with hyperacusis. In this randomized controlled study of 60 patients with hyperacusis, CBT was compared with a waiting list control group using the Loudness Discomfort Level test (LDL), the Hyperacusis Questionnaire, the Hospital Anxiety and Depression Scales, the Quality of Life Inventory and an adapted version of the Tampa Scale of Kinesiophobia. There were significant between-group effects in favour of the CBT group on all measures except for the HADS anxiety scale. Between-group effect sizes were moderate to high, with Cohen's d = 0.67 and 0.69 per ear, respectively, for the primary measure LDL, and ranging from d = 0.32 to 1.36 for the secondary measures. The differences between groups ceased to exist when the waiting list group was treated later with CBT, and the treatment results were largely maintained after 12 months. In conclusion, CBT is a promising treatment for hyperacusis, although more research is necessary.