This report highlights a rare presentation of vitamin B-12 deficiency (concurrent psychotic disorder, seizures and hypertension). A 16-year-old girl presented with nervousness that had been persisting for 2 weeks. She had stopped eating and there was decreased self-care and she could not walk and sleep. Two days prior to admission, generalized tonic clonic convulsions were noted. On physical examination, vital signs were normal, except for hypertension (150/100 mm Hg). She did not respond to conversation; she could not answer the questions. Mood was depressive and hallucinations were noted. Laboratory analyses were normal, except for a low vitamin B-12 level (<150 pg mL(-1)). The patient was not given any treatment of hypertension, psychosis or seizures, except vitamin B-12 injections. After that, she showed improvement within 1 week. In the 7 days of hospitalization, the arterial blood pressure returned to normal, psychotic symptoms were resolved, the visual hallucinations and the depressive mood subsided, and she could eat and speak clearly. No hypertension or convulsions have been detected on the control examinations, and she has now been followed-up without any symptoms or findings. In conclusion, with this report we emphasized that psychosis, seizures and hypertension can be a rare manifestation of vitamin B-12 deficiency, which is reversible with therapy and serum vitamin B-12 level should be checked in patients who do not have an obvious cause for psychosis, seizures or hypertension.