A 32-year-old nulligravid being treated for urinary tract infection presented with disorientation and difficulty in sleeping. She had a normal initial physical examination and her vital signs were stable. Neurologic examination showed subtle signs of impairment in mental state. The patient was admitted at a tertiary medical institution with an impression of acute confusional state, transient global amnesia and urinary tract infection. Twenty-four hours after admission, the patient became restless and disoriented and had delusions and hallucinations. Computer Tomography (CT) scan and trans rectal ultrasound showed a left ovarian newgrowth, probably a dermoid cyst. With the neuropsychiatric manifestations, ovarian teratoma and the patient's disease presentation, anti-N-methyl-O-aspartate receptor (Anti-NMOAR) encephalitis was highly suspected. The patient's serum and cerebrospinal fluid sent for immunomodulatory testing were positive for anti-NMOAR antibodies, confirming the diagnosis. To the best of our knowledge, this is the only recorded case of anti-NMOAR encephalitis with ovarian teratoma in the Philippines. The importance of the case lies in the timely diagnosis and the classical manifestation of the disease that was seen during the patient's stay at the hospital.