We here report one case of hemichorea and Broca aphasia occurred with diabetic ketoacidosis. A 20-year-old woman with type 1 diabetes mellitus had experienced diabetic ketoacidosis fourth time after the onset of diabetes. At the third ketoacidotic episode, the patient was admitted to our hospital for the first time to show hemichorea of the left extremities. Brain computed tomography (CT) demonstrated a high-density area in the right caudate head and low-density area in the right putamen. Magnetic resonance angiography (MRA) demonstrated a stenosis at the root of the bilateral middle and anterior cerebral arteries. The hemichorea disappeared within 3 days. At the fourth ketoacidotic episode, not hemichorea but unconsciousness was there for 2 days even after ketoacidosis disappeared. After the unconscious state, Broca aphasia was demonstrated for 15 days. The cerebral angiography showed a finding compatible to Moyamoya disease. These findings support that chorea and Broca aphasia induced by diabetic ketoacidosis was developed in addition to blood vessel abnormalities such as Moyamoya disease. We suggest that poorly controlled diabetic patients with hemichorea should undergo cerebral angiography.