This study aims to investigate the preventive effect of oral nicorandil on contrast-induced nephropathy (CIN) in patients with renal insufficiency undergoing elective cardiac catheterization. A total of 240 patients with an estimated glomerular filtration rate (eGFR) of 60 mL/min or less, who were undergoing elective cardiac catheterization, were randomly assigned to nicorandil group (n = 120, 10 mg nicorandil, three times daily from 2 days before to 3 days after procedure) or control group (n = 120, matching placebo as the same method). The primary endpoint was the incidence of CIN defined as 25 % increase in serum creatinine (SCr) from baseline or 44 μmol/L (0.5 mg/dL) increase in absolute value within 72 h after exposure to contrast medium. The secondary endpoints were: (1) the changes of SCr, Cystatin-C (Cys-C) and eGFR within 72 h; (2) major adverse events (MACE) occurring within 30 days. Baseline characteristics of the patients in the two groups were similar. The incidence of CIN was significantly lower in nicorandil group compared with control group (6.67 vs. 17.5 %, P = 0.017). Compared with the control group, nicorandil group tended to have a lower SCr and Cys-C levels as well as a higher eGFR at 48 h after the procedure (all P < 0.05). There was no difference about the incidence of MACE within 30 days between nicorandil group and control group (4.16 vs. 5.83 %, P = 0.767). Multivariate logistic analysis showed that nicorandil was an independent protective factor against CIN (OR = 0.260, 95 % CI = 0.1–0.676, P = 0.006). Therefore, we concluded that oral nicorandil was associated with a decline in the incidence of CIN in patients with renal insufficiency undergoing elective cardiac catheterization.