The prognostic value of the geriatric nutritional risk index (GNRI) in patients undergoing percutaneous coronary intervention (PCI) with rotational atherectomy (RA) remains unknown. Therefore, we aimed to clarify whether the GNRI could predict major adverse cardiac events (MACE) in patients undergoing PCI with RA. A total of 206 patients who underwent PCI with RA from January 2009 to December 2017 were retrospectively tracked. The patients were divided into 2 groups based on the GNRI value on admission. MACE comprised all-cause death, target lesion revascularization (TLR), target vessel revascularization (TVR), and myocardial infarction. One year of follow up was completed in 95.6% of patients. During this period, 50 cases of MACE were observed (all-cause death, 32 cases; TLR, 21 cases; and TVR, 2 cases). Patients with a low GNRI (< 98) had a significantly higher incidence of MACE than did patients with a high GNRI (≥ 98) (37.9% vs. 15.5%, log-rank p < 0.05). The GNRI was an independent predictor of MACE (hazard ratio, 0.94; 95% confidence interval [CI], 0.92–0.97). Furthermore, the GNRI had better predictive power than did its components alone (i.e. body mass index and serum albumin level) (net-reclassification improvement, 0.39; 95% CI, 0.07–0.71; p = 0.01; integrated discrimination improvement, 0.02; 95% CI, − 0.01–0.04; p = 0.07). The GNRI on admission is a predictor of MACE after PCI with RA. Further studies are required to determine whether intensive medical therapy could improve clinical events, particularly cardiovascular death and revascularization, in this population.