A craniopharyngioma is a rare, slow-growing tumour in the pituitary gland. Brain tumours usually present with obvious neurological or other physical symptoms, whereas psychiatric symptoms as primary signs are rare. The presented case, in which psychosis and behavioural problems predominated, concerned a 42-year-old patient. Although the tumour was very large when diagnosed, there were no prior neurological signs or signs in the blood sample. Final imaging and histology confirmed the diagnosis of a craniopharyngioma. This case indicates the importance of being sufficiently alert as a psychiatrist when patients are admitted.