BACKGROUND: Exercise has considerable effects on physical and psychological health. Anxiolytic effects of climbing exercise have been found in people suffering from depression. However, there are no studies on patients with severe anxiety disorders or post-traumatic stress disorder (PTSD) practicing climbing as add-on treatment. Additionally, many studies on physical therapy fail to use adequate active control groups. Therefore, this study aimed to investigate the feasibility of a four-week climbing exercise program for patients with anxiety disorders or PTSD in comparison to a standard exercise treatment and a social control group. METHODS: Outpatients diagnosed with anxiety disorders or PTSD (F 40, F 41, F 43.1 according to ICD-10) were randomly assigned to (a) climbing exercise (n = 27), (b) Nordic walking exercise (n = 23), or (c) control condition (n = 23) providing the same amount of social contact for eight sessions of 90 minutes each. Psychological parameters (symptom severity, worry symptoms, self-efficacy, quality of life) and biological parameters were assessed at the beginning and at the end of the four-week program. Additionally, follow-up assessments were conducted three and six months after the program ended. RESULTS: Sixty outpatients (75% female) aged 18-65 years with a longstanding history of a mental disorder (>10 years) and classified as treatment-resistant (95%) and with averaging 3.8 psychiatric comorbidities completed the pilot trial. After participation, symptoms of anxiety disorders were significantly reduced ( CONCLUSIONS: Participation in the climbing group as well as in Nordic walking and social contact groups demonstrated beneficial results in patients with anxiety disorders and PTSD with severe mental burden. Nevertheless, climbing did not show any additional clinically relevant benefits compared to Nordic walking or social contact. Studies with larger sample sizes and qualitative insights are needed to further evaluate the possible benefits of climbing in this population.