This case example illustrates how Acceptance and Commitment Therapy (ACT) within a behavior medicine approach was used in the rehabilitation of an adolescent with debilitating chronic pain. For chronic pain with unclear etiology (idiopathic pain), pharmacological therapy alone is often insufficient. Psychological treatment strategies have been developed and evaluated for adults with chronic pain. However, few such studies have been conducted with youths. To date, there is limited empirical evidence regarding the effectiveness of psychological treatment for generalized musculoskeletal pain syndromes in children and adolescents. This patient was a 14-year-old girl severely disabled by idiopathic generalized pain. It was hypothesized that avoidance of pain and pain-related stimuli was central to the subject's disability. ACT, a development of cognitive behavior therapy, was used as the treatment model in this study, focusing on building the behavior repertoire in valued life directions rather than emphasizing reductions in pain and distress. As the subject moved in valued directions, exposure to avoided pain stimuli took place naturally. Following treatment, improvements in valued life activities and functional ability was seen, as evidenced by increased school attendance, lower pain ratings, and individual goal achievement. The outcome of this treatment indicates that ACT and a behavioral medicine approach can be useful in the rehabilitation of young people with chronic disabling pain. Empirical studies are needed to investigate the clinical effectiveness of this approach.