Diabetic muscle infarction (DMI) is a rare complication of long-standing poorly controlled diabetes mellitus. We herein describe the case of a 56-year-old man with a 10-year history of poorly controlled type 2 diabetes mellitus with multiple microvascular and macrovascular complications who presented with the sudden onset of left thigh pain and swelling. MRI suggested muscle infarction. A muscle biopsy demonstrated coagulation necrosis in the skeletal muscle with inflammation and infarction in the walls of small blood vessels. Physicians should consider DMI in the differential diagnosis of patients with diabetes who present with painful, swollen muscles without systemic signs of infection.