Malignant otitis externa is an invasive infection of the external auditory canal and temporal bone with potentially life-threatening complications. Elderly patients with type 2 diabetes mellitus are the population most commonly affected by malignant otitis externa, but any type of immunosuppression predisposes to the disease. Prader-Willi syndrome is a genetic cause of obesity, often associated with insulin resistance and type 2 diabetes mellitus. This report describes a case of a 21-year-old male patient with Prader-Willi syndrome who had malignant otitis externa that progressed to sepsis during hospitalization. To the best of the authors' knowledge, this is the first description of malignant otitis externa in a young patient with Prader-Willi syndrome.