The number of elderly patients with type 2 diabetes Mellitus (T2DM) is increasing. Such patients show a high rate of renal dysfunction in connection with aging. The selection of appropriate medicines and dosage adjustment are needed to avoid serious hypoglycemia. This study aimed to evaluate the efficacy of Linagliptin, a DPP-4 inhibitor that is primarily excreted by bile. Thirty-nine T2DM patients who were 75 years of age or older and who were newly treated with Linagliptin, who were treated with Linagliptin as an add-on to conventional anti-diabetic therapy, or who were switched to Linagliptin from other DPP-4 inhibitors (i.e., Sitagliptin, or Vildagliptin), were included in the present study. The changes in their blood glucose, renal and liver function, and serum lipid levels were investigated. The patients' blood glucose and HbA1c levels of all patients improved for 3.6 months. The renal function was not affected by treatment and the patients showed no significant change in their body weight. No hypoglycemia or other side effects occurred. In conclusion, Linagliptin had beneficial effects and could be used safely in the treatment of elderly T2DM patients with functional disorders.