This study tested whether inattentive–impulsive–overactive (I/O) and oppositional-defiant (O/D) behaviors were associated with peer problems and whether these associations were moderated by callous–unemotional (CU) traits in clinically referred children with disruptive behaviors. Parents of 135 children aged 6–12 years (M = 9.09, SD = 1.62) completed measures to assess their child’s I/O, O/D, and CU behaviors, and peer functioning problems. Findings showed that I/O and O/D behaviors were associated with greater peer problems, and CU traits significantly moderated the I/O behaviors and peer problems association. Children with relatively more CU traits and I/O behaviors showed greater peer problems. However, those with more CU traits and fewer I/O behaviors showed less peer problems. I/O behaviors and CU traits have an important influence on peer functioning that varies according to the severities of each.