Electrocardiogram (ECG) findings of left ventricular hypertrophy (LVH; ECG-LVH) are observed in patients with dilated cardiomyopathy (DCM), but the prognostic importance is unclear. The present study assessed the impact of QRS voltage on long-term outcomes, including mortality and rehospitalization, in patients with DCM using a database of patients hospitalized for worsening heart failure (HF). We analyzed a total of 261 patients with DCM in the Japanese Cardiac Registry of Heart Failure in Cardiology (JCARE-CARD), a prospective cohort studying the characteristics and treatments in a broad sample of HF patients. ECG-LVH were diagnosed according to the Sokolow-Lyon voltage criteria. A total of 81 patients (31.0%) had ECG-LVH. During a mean follow-up period of 1.8 years, patients with ECG-LVH had a lower rate of all-cause death (9.0% vs. 20.3%, P=0.029) and composite of all-cause death and rehospitalization due to worsening HF (26.9% vs. 45.9%, P=0.007) than those without it. After multivariable adjustment, ECG-LVH was an independent negative predictor for the risk of composite all-cause death and rehospitalization (hazard ratio, 0.358; 95% CI: 0.157-0.857, P=0.049). ECG-LVH were independently associated with better long-term outcome in patients with DCM.