Fear of pain plays an important role in the maintenance of chronic pain. It may be reduced through exposure therapy. This 2-arm parallel samples randomized controlled trial aimed to investigate whether interoceptive exposure (IE) therapy enhances reductions in fear of pain (primary outcome), pain (pain intensity, pain-related disability, and school absence), and emotional characteristics (anxiety and catastrophizing) when implemented as an adjunctive treatment in the context of intensive interdisciplinary pain treatment for pediatric chronic pain patients. N = 126 adolescents, aged 11 to 17 years, who were receiving standard intensive interdisciplinary pain treatment were randomly assigned to either receive additional IE (n = 64) or additional relaxation therapy (RT) (n = 62). All patients were assessed at admission, discharge, and 3 months after discharge. The data of N = 104 patients were analyzed. Significant large reductions were found in the total score and subscale scores of the Fear of Pain Questionnaire for Children in both study groups (eg, total score [range 0-60; IE/RT]: admission M = 23.5/24.9; discharge M = 16.0/19.7; P < 0.001, (Equation is included in full-text article.)= 0.27) and mainly large reductions in pain characteristics. There were no greater decreases in the IE group (P > 0.1). The exploratory analyses revealed that the patients with high fear of pain before treatment (P < 0.05, (Equation is included in full-text article.)> 0.03) and the patients with abdominal pain (P < 0.04, (Equation is included in full-text article.)> 0.25) showed greater decreases in their fear of pain (total and subscale score) in the IE group than in the RT group. In conclusion, the results suggest that IE is not particularly effective for all the pediatric chronic pain patients, but the patients with high fear of pain before treatment and with abdominal pain strongly benefit from this intervention.