Background We report two similar cases of patients diagnosed with hemiballismus–hemichorea syndrome secondary to uncontrolled hyperglycemia. Both patients were treated at an inpatient rehabilitation center and made a significant recovery in both function and activities of daily living. Although hemiballismus–hemichorea syndrome has known pharmacological treatments, little has been reported on the effectiveness of acute rehabilitation on managing and treating this syndrome. Case presentation The first case involves a 44-year-old Hispanic male with past medical history of type 2 diabetes mellitus, hypertension, anxiety, and depression who presented with continuous, uncontrollable, unilateral movements 1 month following a hospital admission for hyperglycemia. Magnetic resonance imaging findings showed lesions in the basal ganglia, confirming the diagnosis of hemiballismus–hemichorea syndrome. The patient was started on antipsychotic medications and antihyperglycemic medications controlling glucose levels, but continued to have hemiballismus symptoms. The second case involves a 78-year-old Haitian female with past medical history of type 2 diabetes mellitus and hypertension who presented with weakness and continuous, involuntary movements in her upper and lower extremities 1 month following a hospital admission for hyperglycemia and encephalopathy. Magnetic resonance imaging findings were positive for bilateral lesions in the basal ganglia, establishing a diagnosis of hemiballismus–hemichorea syndrome. After a 2-week stay at an acute rehabilitation center, both patients made a significant recovery in function and activities of daily living. Conclusion The aim in presenting these cases is to elucidate the etiology and progression of a rare disease process known as hemiballismus–hemichorea syndrome and to provide evidence for the potential positive impact of acute rehabilitation on patients with unresolved hemiballismus–hemichorea following an episode of hyperglycemia.