The relationship between different sleep disturbances and self-harm thoughts and behaviors was examined among 223 adolescents presenting to a community clinic for mood disorders and suicidal and nonsuicidal self-injurious behaviors. Two-thirds of the adolescents reported nightly, severe sleep complaints. Relative to adolescents without significant sleep complaints, patients with severe sleep complaints at the time of clinic entry endorsed significantly more engagement in nonsuicidal self-injury. Middle insomnia and circadian reversal were both significant predictors of suicide attempts. Terminal insomnia was significantly associated with suicidal ideation. Results support the importance of assessing sleep difficulties among adolescents at risk for suicide.