The refeeding syndrome encompasses the complex physiologic state that occurs in malnourished patients who receive nutrition after a period of decreased oral intake. The hallmark of the syndrome is hypophosphatemia, though other electrolyte imbalances and severe fluid shifts are commonly involved. Patients with newly diagnosed malignancies and those undergoing treatment for malignancies are at increased risk for developing the refeeding syndrome, however there are few reported cases or other data in the oncology literature regarding this syndrome in cancer patients.