Behavioral pain assessment is possible for children and youth with intellectual and developmental disabilities (IDD). However, pain behavior is often misinterpreted as reflecting psychopathology. We examined whether psychopathology alters pain behavior. Caregivers of 123 children (56 girls ages 40 to 258 months) completed the Non-Communicating Children's Pain Checklist-Revised (NCCPC-R) to assess pain behavior and the Diagnostic Assessment for the Severely Handicapped-II to assess psychopathology. Seventy-eight children had clinically significant psychological or behavioral symptoms. A principal components analysis revealed 3 independent components: Pain Behavior, Affective Disorders, and Developmental Disorders. The results indicate that psychopathology has little effect on pain behavior and that the NCCPC-R is suitable for children with IDD who also have psychological or behavior disorders. (Contains 5 tables.)