New-onset psychotic symptoms presenting late in life can be caused by various medical and psychiatric conditions. The index of suspicion for an organic cause for psychotic symptoms in an elderly person should be high, and every presenting patient should undergo a detailed history-taking and evaluation before attributing these symptoms to a primary psychiatric condition. Hyperparathyroidism is one condition that can present with psychiatric symptoms such as low mood and anxiety. While psychiatric symptoms are not uncommon in hyperparathyroidism, acute psychosis is rare. This case report highlights the importance of a thorough evaluation of an elderly person presenting with a new onset of psychosis.