: Vildagliptin is a dipeptidyl peptidase-4 inhibitor that reduces glycemia in patients with type 2 diabetes mellitus (T2DM). When approved in 2013, data on vildagliptin combined with >750 mg/day metformin in Japanese patients were limited. There is a need to confirm the safety and efficacy of vildagliptin in combination with oral antidiabetic drugs (OADs).: This 52-week post-marketing surveillance (PMS) observational study in Japanese T2DM patients evaluated the safety and efficacy of vildagliptin in combination with OADs including high-dose metformin or insulin but excluding combination with sulfonylureas alone.: During this survey of 3006 Japanese T2DM patients, 13.61% of patients experienced adverse events (AEs) and 2.20% reported a serious AE (SAE). The frequency of AEs/SAEs was similar when in combination with biguanides (12.93%/1.46%), metformin ≥1000 mg/day (12.92%/1.22%), metformin <1000 mg/day (12.62%/1.54%), thiazolidine derivatives (16.71%/2.86%), α-glucosidase inhibitors (13.18%/1.90%), rapid-acting insulin secretagogues  (glinides) (20.41%/5.71%), or insulin (15.87%/2.47%). The mean ± SD changes from baseline at endpoint in glycated hemoglobin and fasting blood glucose were -0.76 ± 1.27% and -23.3 ± 57.3 mg/dL, respectively, and these changes were consistent, regardless of concomitant OAD.: Long-term vildagliptin combination therapy is safe and effective in Japanese T2DM patients in real-world settings.