We report the case of a 13-year-old boy with poorly controlled type 2 diabetes mellitus who developed severe diabetic amyotrophy, which progressed over a few months but demonstrated rapid recovery after administration of intravenous immunoglobulin. This report highlights the importance of monitoring adolescents for even the rare neurologic complications of diabetes mellitus most commonly encountered in adults, and supports the need for well-designed trials using immunomodulatory therapies in diabetic amyotrophy.