Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is a common cause of autoimmune encephalitis. The condition is difficult to diagnose or suspect in the emergency department because it usually presents with nonspecific neurological or psychiatric symptoms. It is often mistaken for viral encephalitis or psychiatric illness. This paper reports a case of anti-NMDAR encephalitis in which the patient experienced mood changes, including suicidal ideation, which led to a delayed diagnosis after three visits to the emergency department. This paper aims to raise awareness among emergency physicians about the possibility of anti-NMDAR encephalitis and to encourage them to consider it in their differential diagnosis in the emergency department.