Anti-NMDA receptor encephalitis is an auto-immune disorder often presenting with non-specific and heterogeneous neuropsychiatric symptoms at onset. This complicates a quick and accurate diagnosis. However, a tardy diagnosis has a negative impact on morbidity and mortality. We report about a patient with the clinical presentation of a psychotic depression, who was diagnosed with anti-NMDA receptor encephalitis only after a thorough diagnostic work-up. Neurological symptoms were wrongly attributed to the psychiatric syndrome or considered as side-effects of its treatment. We present an overview of clinical aspects of the disorder, distinctive psychiatric symptoms, diagnostic tools, treatment and prognosis.