This study examined the association of childhood abuse with deliberate self-harm and related psychopathology and the impact of childhood abuse on treatment outcome as assessed in a randomized controlled trial of cognitive-behavioral therapy for 90 young people who recently engaged in Deliberate Self-Harm (DSH). Participants with a history of childhood sexual abuse manifested more Axis I disorders and reported higher levels of DSH, depression, suicidal cognitions, anxiety, and dissociation. After statistically controlling for baseline differences in DSH and related psychopathology, participants with a reported history of childhood sexual abuse showed a significantly lower risk of repeated DSH in the Cognitive-Behavioral Therapy condition compared with those receiving treatment-as-usual (TAU). Our results suggest that a structured treatment format and focus on adequate emotion regulation skills may be essential elements in the treatment of persons with DSH and a history of childhood sexual abuse.