The utility of immunotherapy, such as pembrolizumab, is becoming essential in the treatment of certain cancers. Pembrolizumab works through binding of programmed cell death 1 receptor that blocks the binding of the programmed cell death ligand 1 and is commonly used in non-small cell lung cancer and melanoma. Pembrolizumab has been reported to be associated with multiple adverse reactions such as pneumonitis, colitis, hepatitis, hypophysitis, hyperthyroidism, hypothyroidism, nephritis, and type 1 diabetes; however, pembrolizumab causing type 1 diabetes was only reported in 0.1% of the patients in clinical trials. A review of the literature generated 1,001 unique citations of which six reported cases of autoimmune diabetes associated with pembrolizumab were selected and compared. Review of the cases showed no sexual predilection and the average age of onset was 58 years old. The majority of the patients were treated for melanoma (5/6 cases), initially presented with diabetic ketoacidosis (4/6 cases), and had at one point taken ipilimumab (4/6 cases). There was no association found between the number of treatments received and the development of diabetes. With the increasing use of pembrolizumab in cancer treatment regular blood glucose monitoring during treatment, especially in patients who had also taken ipilimumab, may prevent the onset of this life-threatening complication.