Introduction The aim of this study was to compare the efficacy of vildagliptin as add-on therapy to short-term continuous subcutaneous insulin infusion (CSII) with CSII monotherapy in hospitalized patients with type 2 diabetes mellitus (T2DM). Methods A total of 200 hospitalized patients with inadequately controlled T2DM were randomized into groups, with one group receiving CSII monotherapy (CSII group, n =100) and the other group receiving CSII plus vildagliptin as add-on (CSII + Vig group, n = 100). Of these, 191 completed the 7-day trial (CSII group, n = 99; CSII + Vig group, n = 92) and included in the analysis. The glycemic control and variability of the patients were measured using all-day capillary blood glucose (BG) monitoring. Weight and fasting C-peptide levels were evaluated before and after the interventions. Results Mean BG concentrations during the whole treatment period were lower and the time to reach target BG was reduced in the CSII + Vig group compared with the CSII group (9.89 ± 3.37 vs. 9.46 ± 3.23 mmol/L, P