Diarrhea is a distressing symptom that limits the quality of life in terminally ill patients. In these patients, many factors can affect intestinal secretion, absorption, and motility, including drugs, infective agents, antibiotics, chemotherapy, radiotherapy, surgery, malnutrition, neuroendocrine tumors, and mechanical bowel obstruction. Diarrhea can result in water and electrolyte losses. This review discusses the pathophysiology, assessment, and treatment of diarrhea in advanced cancer patients.