Mental health disorders in adolescence are a significant problem, relatively common, and amenable to treatment or intervention. Obstetrician–gynecologists who see adolescent patients are highly likely to see adolescents and young women who have one or more mental health disorders. Some of these disorders may interfere with a patient’s ability to understand or articulate her health concerns and appropriately adhere to recommended treatment. Some disorders or their treatments will affect the hypothalamic–pituitary–gonadal axis, causing anovulatory cycles and various menstrual disturbances. Adolescents with psychiatric disorders may be taking psychopharmacologic agents that can cause menstrual dysfunction and galactorrhea. Adolescents with mental illness often engage in acting-out behavior or substance use, which increases their risk of unsafe sexual behavior that may result in pregnancy or sexually transmitted infections. Pregnant adolescents who take psychopharmacologic agents present a special challenge in balancing the potential risks of fetal harm with the risks of inadequate treatment. Whether providing preventive women’s health care or specific obstetric or gynecologic treatment, the obstetrician–gynecologist has the opportunity to reduce morbidity and mortality from mental health disorders in adolescents by early identification, appropriate and timely referral, and care coordination. Although mental health disorders should be managed by mental health care professionals or appropriately trained primary care providers, the obstetrician–gynecologist can assist by managing the gynecologic adverse effects of psychiatric medications and providing effective contraception and regular screening for sexually transmitted infections. This Committee Opinion will provide basic information about common adolescent mental health disorders, focusing on specific implications for gynecologic and obstetric practice.