Background: Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis represents a paradigmatic form of autoimmune encephalitis characterized by a constellation of neuropsychiatric symptoms including psychosis, seizures, cognitive dysfunction, and movement disorders. This condition poses significant diagnostic challenges due to its multifaceted clinical presentation that often mimics primary psychiatric disorders. Objective: To examine the complex diagnostic and therapeutic considerations in a patient presenting with acute-onset psychosis and seizures secondary to anti-NMDAR encephalitis, emphasizing the critical importance of early recognition and multidisciplinary management. Case Summary: We present a 43-year-old postpartum female who developed severe neuropsychiatric symptoms including acute psychosis, seizures, and cognitive impairment. Initial psychiatric evaluation suggested a primary psychotic disorder; however, the presence of seizures, cognitive dysfunction, and a concurrent ovarian teratoma prompted reconsideration of the diagnosis. Cerebrospinal fluid analysis confirmed the presence of anti-NMDAR antibodies. Treatment with first-line immunotherapy (corticosteroids), antiepileptic drugs (valproic acid), and antipsychotics (aripiprazole) resulted in partial symptomatic improvement with persistent residual deficits. Clinical Significance: This case underscores the importance of maintaining high clinical suspicion for autoimmune encephalitis in patients presenting with new-onset psychosis, particularly when accompanied by seizures, cognitive dysfunction, or evidence of systemic autoimmunity. Early diagnosis and prompt initiation of immunotherapy are crucial for optimal neurological and psychiatric outcomes.