Understanding of the mechanisms by which cancer cells evade T-cell immunity through interaction with a number of ligands has led to the introduction of immunotherapy. Immune checkpoint inhibitors prevent T-cell deactivation by malignant cells enhancing the anticancer immune response. Agents acting on CTLA-4 and PD-1, and its ligand are the principal therapeutic immunotherapy drugs in practice. These agents are potent and are now used in a variety of malignancies. Activation of the immune system results in risk of adverse effects, particularly affecting the skin, GI tract, and endocrine system. This review addresses the endocrine toxicities seen with immunotherapy. Thyroid, pituitary, and adrenal diseases are most common. Diabetes, as a result of islet-cell destruction, also occurs as do rarer endocrinopathies. Differences in rates and patterns of endocrine complications are seen with the CTLA-4 and PD-1 acting agents. This chapter summarizes the endocrine consequences of immunotherapy and provides guidance on the management of these common conditions.