Immune checkpoint inhibitors (ICIs) are regarded as a break-through discovery and are used in regimens for treating patients with various malignancies, inducing activated T-cells to kill cancer cells; however, the safeguard autoimmune systems that are “checked and halted” in function before the use of ICIs, are re-activated after terminating the treatment. Thus, during the treatment course ICIs may stimulate and activate the development of various autoimmune disorders, mostly related to endocrine organs including the pituitary gland, thyroid gland, adrenal gland, and endocrine pancreas. The endocrine dysfunctions induced by ICI treatment include central adrenal insufficiency (AI) and central hypothyroidism related to hypophysitis of the adenohypophysis, primary hypothyroidism related to thyroiditis, and insulin-dependent diabetes mellitus (IDDM) caused by β-cell destruction in the endocrine pancreas. With the increasing use of ICIs, these immune-related adverse events have been observed as a prominent clinical entity that deserves clinical vigilance with respect to timely diagnosis and optimal treatment in addition to treating the underlying malignancies. These endocrine dysfunctions may not be readily diagnosed because of the insignificant clinical symptoms and signs presented. However, with such cases being increasingly recognized and reported, it would be prudent for physicians to regard these potential endocrine disorders as important in their daily practice when ICI-containing regimens are used. At any suspicion from vague clinical presentations, laboratory tests relevant to endocrine functions must be promptly performed to confirm a diagnosis. Treatment including measures of either replacement or suppression of disease characteristics should then be initiated and monitored regularly.