Aim Assess long‐term safety and efficacy of the dipeptidlyl peptidase-4 (DPP‐4) inhibitor vildagliptin in 369 patients with type 2 diabetes mellitus (T2DM) and moderate or severe renal impairment (RI). Methods Double‐blind, randomized, parallel‐group, 52‐week clinical trial comparing safety and efficacy of vildagliptin (50 mg qd, n = 216) and placebo (n = 153) added to ongoing stable antihyperglycaemic treatment, in patients with T2DM and moderate or severe (glomerular filtration rate GFR ≥30 to <50 ml/min/1.73 m2and < 30 ml/min/1.73 m2) RI. Results The study population comprised 122 and 89 patients with moderate RI and 94 and 64 patients with severe RI randomized to vildagliptin and placebo, respectively, with the majority of patients receiving background insulin therapy (72% and 82% for moderate and severe RI, respectively). After 1 year, the between‐treatment difference in adjusted mean change in A1C was −0.4 ± 0.2% (p = 0.005) in moderate RI (baseline = 7.8%) and −0.7 ± 0.2% (p < 0.0001) in severe RI (baseline = 7.6%). In patients with moderate RI, similar proportions of patients experienced any adverse event (AE) (84 vs. 85%), any serious adverse event (SAE) (21 vs. 19%), any AE leading to discontinuation (5% vs. 6%) and death (1% vs. 0%) with vildagliptin and placebo, respectively. This was also true for patients with severe RI: AEs (85% vs. 88%), SAEs (25% vs. 25%), AEs leading to discontinuation (10% vs. 6%) and death (3% vs. 2%). Conclusions In patients with T2DM and moderate or severe RI, vildagliptin added to ongoing antidiabetic therapy had a safety profile similar to placebo during 1‐year observation. Furthermore, relative to placebo, a clinically significant decrease in A1C was maintained throughout 1‐year treatment with vildagliptin.