Mood and anxiety disorders are common in the general population and in the emergency setting. As psychiatric emergency care moves from the realm of triage and referral to a more definitive initiation of treatment, clinicians must approach the assessment and initial management of patients with mood and anxiety disorder in a rational and safe way. In the ED, the next step in assessing patients with mood or anxiety symptoms, after any immediate safety concerns are addressed, is to rule out medical or substance-induced causes. Treatment of these patients is directed at the underlying condition. When a primary psychiatric diagnosis is made, initial management, including definitive pharmacologic or psychotherapeutic intervention, can be started in the ED.