Autoimmune anti-N-methyl-D-aspartate receptor encephalitis was identified in 2007. It is a rare encephalitis (approximately 4%) of the limbic type and is typically diagnosed in young females with paraneoplastic teratomas. Cerebral NMDA receptor blockade leads to characteristic symptoms. GABA neuron inactivation results in psychotic disorders, involuntary movements, fasciculations and nystagmus. Moreover, by affecting the respiratory centre in the brainstem, it can cause respiratory disorders requiring mechanical ventilation. Other symptoms, such as sialorrhea, arrhythmias or arterial hypertension, result from the influence on the autonomous nervous system. NMDA receptor disorders are functional in nature and are mostly reversible. That is why proper diagnosis and prompt treatment, involving tumour removal and immunotherapy, may bring positive therapeutic effects. Approximately 75% of patients with autoimmune anti-NMDA receptor encephalitis have recovered completely or the disease has left only slight consequences. However, it has led to severe deficits in the remaining patients and was fatal in 7% of cases. The paper presents a case of a 23-year-old female with autoimmune encephalitis associated with ovarian teratoma. The disease was diagnosed late and its course was severe with numerous complications and necessity of intensive care. After several months, the patient regained full intellectual functions and intends to continue studying law. The aim of this report was to draw attention to a rare cause of autoimmune encephalitis, which when detected early makes it possible to obtain full recovery. Particular attention should be paid to young women who manifest atypical clinical signs within the central nervous system without tangible changes in imaging. This should prompt the search for a tumour in the abdominal cavity.