Carcinoid tumors are neuroendocrine tumors that mainly arise in the gastrointestinal tract, lungs, and bronchi. Bronchopulmonary carcinoids have been associated with Cushing syndrome, which results from ectopic adrenocorticotrophic hormone (ACTH) secretion. We report the case of a 65-year-old man, a colonel in the US Air Force, with metastatic bronchopulmonary carcinoid tumors treated on a clinical trial who was hospitalized for complaints of increasing thirst, polydipsia, polyuria, weakness, and visual changes. Decompensated hyperglycemia suggested a diagnosis of hyperglycemic hyperosmolar nonketotic syndrome (HHNS). Additional findings, which included hypokalemia, hypernatremia, hypertension, metabolic alkalosis, moon facies, and striae, raised a red flag for an ectopic ACTH syndrome. Elevated ACTH levels confirmed Cushing syndrome. Treatment with a fluid replacement and insulin drip resulted in immediate symptomatic improvement. Cushing syndrome should be considered in carcinoid patients with physical stigmata such as moon facies and striae. HHNS may be the presenting clinical feature in patients with impaired glucose metabolism.