Renal dysfunction is a known risk of sudden cardiac death in patients with ischemic heart disease. However, the association between renal dysfunction and sudden death in hypertrophic cardiomyopathy (HC) patients remains unknown. This study investigated the significance of an impaired renal function for the sudden death risk in a cohort of patients with HC. We included 450 patients with HC (mean age 52.9 years, 65.1% men). The estimated glomerular filtration rate (eGFR) was evaluated at the time of the initial evaluation. Renal dysfunction was defined as an eGFR <60 mL/min/1.73 m2. Renal dysfunction was found in 171 patients (38.0%) at the time of enrollment. Over a median (IQR) follow-up period of 8.8 (5.0-12.5) years, 56 patients (12.4%) experienced the combined endpoint of sudden death or potentially lethal arrhythmic events, including 20 with sudden death (4.4%), 11 resuscitated after a cardiac arrest, and 25 with appropriate implantable defibrillator shocks. Patients with renal dysfunction were at a significantly higher risk of sudden death (Log-rank p =0.034) and the combined endpoint (Log-rank p <0.001) than patients without renal dysfunction. After adjusting for the highly imbalanced baseline variables, the eGFR remained as an independent correlate of the combined endpoint (adjusted hazard ratio: 1.24 per 10 ml/min decline in the eGFR; 95% confidence interval 1.04-1.47; p =0.013). In conclusion, an impaired renal function may be associated with an incremental risk of sudden death or potentially lethal arrhythmic events in patients with HC.