INTRODUCTION: Anti-NMDA receptor (NMDAR) encephalitis is an autoimmune or paraneoplastic disorder commonly associated with ovarian, lung, breast and testicular tumors, or even in patients without a tumor. Clinical manifestations consist mainly in psychiatric disturbances, memory deficits and speech impairment. The diagnosis is performed with detection of anti-NMDAR antibodies in CSF. Imaging studies are important, because 38% of the patients have identifiable tumors in lung, ovary and testicles. Most patients respond well to immunotherapy, tumor removal, or both. CASE REPORT: A 33-year-old woman presented with an acute psychotic episode, initially treated with antipsychotic drugs, then she developed symptoms that suggested neuroleptic malignant syndrome (NMS). Afterwards she presented akinetic mutism, hands tremor, orofacial dyskinesias and seizures. Blood test showed increased levels of serum CK. Head CT and MRI findings were normal. CSF showed pleocytosis. Pelvic CT revealed an image consistent with ovarian teratoma and anti-NMDAR antibodies tested positive in CSF. Treatment was started with immunosuppression, tumor removal and plasmapheresis, showing improvement in 4 weeks. CONCLUSION: This case illustrates that anti-NMDAR encephalitis is a poorly identified entity in our settings. Because patients present with psychiatric symptoms, they can be managed initially with neuroleptic agents, without showing improvement and with the possibility of developing NMS. Despite the severity of the disease, there is a possibility of improvement with intensive care and immunotherapy.