This study explored the impact of comorbidity on symptom severity and treatment outcome in a sample of 75 pediatric Obsessive–Compulsive Disorder (OCD) patients. Forty received cognitive–behavioral therapy (CBT). Overall, 56% had a comorbid disorder. Results revealed that youth with comorbid disorders (anxiety or otherwise) endorsed significantly more anxiety symptoms than youth with OCD only. Youth with comorbidities instead of or in addition to anxiety exhibited more severe OCD symptoms than youth with OCD alone or an anxiety-only comorbidity. Youth in the comorbidities instead of or in addition to anxiety group had the poorest CBT response relative to the other groups. These results suggest that relative to those with OCD alone or with an anxiety disorder comorbidity, youth with comorbidities instead of or in addition to anxiety have a differing clinical presentation (e.g., more severe symptoms) and worse psychotherapy outcome.