This study examined the effects of comorbid ADHD symptoms, internalizing psychopathology, Callous–Unemotional (CU) Traits, and conduct problem severity on children’s response to an evidence-based psychosocial intervention. Clinic-referred children with DBD ages 8–12 years (N = 76) participated in a 15-week multi-component intervention. Parents provided weekly ratings of children’s oppositionality-defiance, peer problems, and impairment. Oppositionality-defiance, peer problems, and impairment decreased significantly over the course of the intervention; however, there was considerable variability in weekly ratings. Baseline ADHD symptoms, internalizing psychopathology, CU traits, and conduct problem severity were unrelated to rate of change across treatment. However, ADHD symptoms uniquely predicted more oppositionality-defiance, peer problems, and impairment averaged across the 15 weeks of treatment. Follow-up analyses suggested this was driven by hyperactivity-impulsivity rather than inattention. Children with DBD and comorbid symptoms appear to benefit from a multi-component intervention, but those with ADHD symptoms may require additional support to address social and behavioral challenges.