Assessing the efficacy of implantable cardioverter-defibrillators (ICD) in patients with Chagas' heart disease (ChHD) and identifying the clinical predictors of mortality and ICD shock during long-term follow-up. ChHD is associated with ventricular tachyarrhythmias and an increased risk of sudden cardiac death. Although ChHD is a common form of cardiomyopathy in Latin American ICD users, little is known about its efficacy in the treatment of this population. The study cohort included 116 consecutive patients with ChHD and an ICD implanted for secondary prevention. Of the 116 patients, 83 (72%) were men; the mean age was 54 ± 10.7 years. Several clinical variables were tested in a multivariate Cox model for predicting long-term mortality. The average follow-up was 45 ± 32 months. New York Heart Association class I-II developed in 83% of patients. The mean left ventricular ejection fraction was 42 ± 16% at implantation. Of the 116 patients, 58 (50%) had appropriate shocks and 13 (11%) had inappropriate therapy. A total of 31 patients died (7.1% annual mortality rate). New York Heart Association class III (hazard ratio [HR] 3.09, 95% confidence interval 1.37 to 6.96, p = 0.0064) was a predictor of a worse prognosis. The left ventricular ejection fraction (HR 0.972, 95% confidence interval 0.94 to 0.99, p = 0.0442) and low cumulative right ventricular pacing (HR 0.23, 95% confidence interval 0.11 to 0.49, p = 0.0001) were predictors of better survival. The left ventricular diastolic diameter was an independent predictor of appropriate shock (HR 1.032, 95% confidence interval 1.004 to 1.060, p = 0.025). In conclusion, in a long-term follow-up, ICD efficacy for secondary sudden cardiac death prevention in patients with ChHD was marked by a favorable annual rate of all-cause mortality (7.1%); 50% of the cohort received appropriate shock therapy. New York Heart Association class III and left ventricular ejection fraction were independent predictors of worse prognosis, and low cumulative right ventricular pacing defined better survival.