Normal-pressure hydrocephalus (NPH) is a common cause of potentially reversible dementia. It can present with psychiatric manifestations that may hinder its diagnosis. A 68-year-old man presented with a paranoid psychosis and mild cognitive impairment, but no neurological signs or classic “triad.” Gait disturbance and urinary incontinence developed later in the course of illness after the diagnosis of NPH had already been made on computed tomographic (CT) scanning. A lumbo-peritoneal shunt was performed, followed by full remission of psychotic symptoms, as well as considerable improvement in functioning, continence, and gait. This case demonstrates the need to consider NPH when older patients present with psychotic symptoms, particularly in the presence of cognitive impairment, gait disturbance, or incontinence. The decision whether to perform a shunting operation is often difficult, because selection of patients with good prognosis is still inaccurate. CT scanning of the brain is an important investigation in older patients presenting with both functional and organic disorders.