The onset of diabetic retinopathy correlates with the long-term quality of glycemic control. A 17-yr-old adolescent with type 1 diabetes presented unexpectedly with acute non-proliferative retinopathy despite good glycemic control. Two months later chronic myeloid leukemia (CML) was diagnosed. Chemotherapy was initiated and within a few weeks the patient was in full remission concerning leukemia. Retinopathy completely resolved within 8 months. The patient was in good metabolic control throughout the course. To our knowledge, this is the first report of CML-triggered retinopathy in a well-controlled diabetic adolescent. In case of unexpected retinopathy in patients with type 1 diabetes, other potential causes of retinopathy should be considered.