The association of ovarian teratoma and anti-N-Methyl-Daspartate receptor (anti-NMDAR) is one of the most common autoimmune encephalitis syndromes and it is a serious and potentially fatal pathology that occurs in young women. This case report describes of a pediatric patient with anti-NMDAR encephalitis. A-12-year-old girl presented with abnormal behavior for one week came to Emergency Department of Sarawak General Hospital, Malaysia. She had psychotic spectrum symptoms including suicidal tendency. She was diagnosed with anti-NMDAR encephalitis as positive antibody was seen in her cerebrospinal fluid. She was treated with Injection Immunoglobulin. She turned out to have teratoma which was successfully removed later. Her progress was remarkable after the surgery with the Immunoglobulin. A multi-disciplinary team involving a psychiatrist, neurologist and gynaecologist liaised with intensivist to successfully manage the case and achieve the good outcome.