Background Arrhythmogenic right ventricular dysplasia/cardiomyopathy is characterized by ventricular arrhythmias and sudden cardiac death. Once the diagnosis is established, risk stratification to determine whether implantable cardioverter‐defibrillator ( ICD ) placement is warranted is critical. Methods and Results The cohort included 312 patients (163 men, age at presentation 33.6±13.9 years) with definite arrhythmogenic right ventricular dysplasia/cardiomyopathy who received an ICD . Over 8.8±7.33 years, 186 participants (60%) had appropriate ICD therapy and 58 (19%) had an intervention for ventricular fibrillation/flutter. Ventricular tachycardia at presentation (hazard ratio [ HR ]: 1.86; 95% confidence interval [ CI ], 1.38–2.49; P <0.001), inducibility on electrophysiology study (HR: 3.14; 95% CI, 1.95–5.05; P <0.001), male sex (HR: 1.62; 95% CI, 1.20–2.19; P =0.001), inverted T waves in ≥3 precordial leads (HR: 1.66; 95% CI, 1.09–2.52; P =0.018), and premature ventricular contraction count ≥1000/24 hours (HR: 2.30; 95% CI, 1.32–4.00; P =0.003) were predictors of any appropriate ICD therapy. Inducibility at electrophysiology study (HR: 2.28; 95% CI, 1.10–4.70; P =0.025) remained as the only predictor after multivariable analysis. The predictors for ventricular fibrillation/flutter were premature ventricular contraction ≥1000/24 hours (HR: 4.39; 95% CI, 1.32–14.61; P =0.016), syncope (HR: 1.85; 95% CI, 1.10–3.11; P =0.021), aged ≤30 years at presentation (HR: 1.76; 95% CI, 1.04–3.00; P <0.036), and male sex (HR: 1.73; 95% CI, 1.01–2.97; P =0.046). Younger age at presentation (HR: 3.14; 95% CI, 1.32–7.48; P =0.010) and high premature ventricular contraction burden (HR: 4.43; 95% CI, 1.35–14.57; P <0.014) remained as independent predictors of ventricular fibrillation/flutter. Complications occurred in 66 participants (21%), and 64 (21%) had inappropriate ICD interventions. Overall mortality was low at 2%, and 4% underwent heart transplantation. Conclusion These findings represent an important step in identifying predictors of ICD therapy for potentially fatal ventricular fibrillation/flutter and should be considered when developing a risk stratification model for arrhythmogenic right ventricular dysplasia/cardiomyopathy.