We investigated hyperglycemia due to atypical antipsychotics in cancer patients with delirium. Using patient records retrospectively, we investigated 189 cancer patients who were diagnosed with delirium between June 2008 and May 2009. One- hundred fifty-four of the 189 patients used atypical antipsychotics for delirium treatment. Three percent(5/154)of them were admitted with over 350 mg/dL blood glucose during their atypical antipsychotics treatment, however, all cases did not relate the adverse reaction of hyperglycemia with the use of antipsychotics. Most cancer patients with delirium used atypical antipsychotics, and the incidence of hyperglycemia was low.