Background Outcomes data in patients with cardiac amyloidosis after implantable cardioverter‐defibrillator (ICD) implantation are limited. We compared outcomes of patients with ICDs implanted for cardiac amyloidosis versus nonischemic cardiomyopathies (NICMs) and evaluated factors associated with mortality among patients with cardiac amyloidosis. Methods and Results Using National Cardiovascular Data Registry’s ICD Registry data between April 1, 2010 and December 31, 2015, we created a 1:5 propensity‐matched cohort of patients implanted with ICDs with cardiac amyloidosis and NICM. We compared mortality between those with cardiac amyloidosis and matched patients with NICM using Kaplan‐Meier survival curves and Cox proportional hazards models. We also evaluated risk factors associated with 1‐year mortality in patients with cardiac amyloidosis using multivariable Cox proportional hazards regression models. Among 472 patients with cardiac amyloidosis and 2360 patients with propensity‐matched NICMs, 1‐year mortality was significantly higher in patients with cardiac amyloidosis compared with patients with NICMs (26.9% versus 11.3%, P <0.001). After adjustment for covariates, cardiac amyloidosis was associated with a significantly higher risk of all‐cause mortality (hazard ratio [HR], 1.80; 95% CI, 1.56–2.08). In a multivariable analysis of patients with cardiac amyloidosis, several factors were significantly associated with mortality: syncope (HR, 1.78; 95% CI, 1.22–2.59), ventricular tachycardia (HR, 1.65; 95% CI, 1.15–2.38), cerebrovascular disease (HR, 2.03; 95% CI, 1.28–3.23), diabetes mellitus (HR, 1.55; 95% CI, 1.05–2.27), creatinine = 1.6 to 2.5 g/dL (HR, 1.99; 95% CI, 1.32–3.02), and creatinine >2.5 (HR, 4.34; 95% CI, 2.72–6.93). Conclusions Mortality after ICD implantation is significantly higher in patients with cardiac amyloidosis than in patients with propensity‐matched NICMs. Factors associated with death among patients with cardiac amyloidosis include prior syncope, ventricular tachycardia, cerebrovascular disease, diabetes mellitus, and impaired renal function.