A retrospective chart review was used to examine sexual behavior (hypersexual, exposing, and victimizing) and cognitive impairment in 200 youth who had serious mental illness. Lower IQ was associated with increased sexual acting-out. For more serious victimizing sexual behaviors, only Verbal IQ differences reached statistical significance. Overall, sexual behavior was strongly associated with a history of sexual abuse. Sexual abuse history was significantly associated only with lower Performance IQ. Therefore, the association between low Verbal IQ and sexual victimizing behavior is distinct from the effects of sexual abuse. Results underscore the importance of verbal cognitive abilities, regardless of overall cognitive level, in the etiology and treatment of sexual behaviors, especially among individuals without a history of sexual abuse.