Delirium is considered to be multifactorial, especially in elderly patients and those with advanced cancer, and can cause significant distress. High baseline vulnerability at the end of life, combined with cachexia, hepatic impairment, general comorbidities, and impaired functional status, can make delirium difficult to correct. Nonetheless, approximately 50% of delirium episodes are potentially reversible and reversible causes should be investigated. Hypercalcemia is one of the reversible metabolic causes of delirium in patients with advanced cancer. Here, we present the case of a patient with metastatic small cell prostate carcinoma who presented to our palliative care clinic with uncontrolled symptoms. A thorough evaluation using appropriate assessment tools revealed that he had delirium, and hypercalcemia was found to be the major etiologic factor. An interdisciplinary team approach (including a nutritionist, pharmacist, counselor, social worker, chaplain, and case manager) was provided. With aggressive symptom management and correction of hypercalcemia and other reversible causes of delirium, the delirium was resolved and the symptoms were controlled. This case illustrates the importance of screening for delirium in patients with severe symptom distress and how the interdisciplinary management of reversible causes of delirium, including hypercalcemia, can improve patients' symptoms and quality of life.