Choreoathetosis is a rare neurologic complication of the diabetic disease. The purpose of this case report is to increase the knowledge of such occurrence by describing the case of an elderly woman who was admitted to our institution for an over 20-day history of choreic movement in the left side of the body. She had a 6-year history of type 2 diabetes mellitus with a poor metabolic control including a glycosylated hemoglobin of 13%. Unenhanced computed tomography of the brain was negative. At magnetic resonance imaging, the right putamen showed high signal intensity on T1-weighted images and an area of high signal intensity on T2-weighted images, diffusion-weighted images and apparent diffusion coefficient maps. During the hospitalization, an adequate diet therapy was performed, and insulin therapy was gradually adjusted using regular insulin at main meals associated with basal insulin (glargine) "bed time". This resulted in progressive normalization of blood glucose values and an improvement of dyskinesia. There is a deep correlation between non-chetotic hyperglycemia and neurologic lesions leading to choreoathetosis. The etiopathogenesis seems multifactorial, and include hyperosmolar damage on cortical cells, alteration in GABA neurotransmission and in cerebral vascular self-regulation mechanism. Notably, in DM type 2 choreoathetosis may be related to both vascular and neuro-metabolic alterations in the basal nucleus due to inadequate glycemic control continuing in the time. This rare complication of DM type 2 is a pathological entity to be considered benign, since it is generally transient and reversible with the attainment of an adequate metabolic compensation.