Anti-N-methyl D-aspartate receptor (NMDAR) encephalitis is a rare condition, often associated with neoplasms and characterized by neuropsychiatric symptoms and dysautonomia. Affecting approximately 0.01% of cancer patients, it is the second most frequent autoimmune encephalitis after acute disseminated encephalomyelitis, its clinical presentation is usually acute and severe, so prompt identification and treatment improve prognosis. We present the case of a 23-year-old female patient from a rural area of Caquetá, Colombia, previously healthy, who presented persistent psychotic symptoms of two weeks of evolution and was initially treated in a psychiatric unit where she evolved with systemic compromise. Finally, a diagnosis of paraneoplastic anti-NDMAR encephalitis was made. The patient received IV immunoglobulin G plus adjuvant systemic management with chemotherapy. She had complete resolution of her neuropsychiatric disorder and was asymptomatic when discharged. In conclusion, anti-NMDAR encephalitis is a condition with an underlying autoimmune mechanism, with production of autoantibodies mainly against the NR1 and NR2 subunits of NMDA receptors in the brain. These autoantibodies are produced in response to a breakdown of immune tolerance usually secondary to a neoplastic process, mostly ovarian teratoma, or infectious as in the case of herpes viral encephalitis. Despite its severe and potentially fatal nature, AE typically exhibits a positive response to treatment if a prompt diagnosis is established and management is initiated. However, it is acknowledged in some texts that there is still a gap in recognizing this entity, which encourages future valuable research.