Children at high risk for sudden cardiac death (SCD) receive implantable cardioverter-defibrillators (ICD) for prevention, but the cost effectiveness of ICDs in children at intermediate risk is unclear. Our objective was to create a cost-effectiveness model to compare costs and outcomes in children at risk of SCD, with and without ICD. Utilizing hypertrophic cardiomyopathy as the proxy disease, a theoretical cohort of 8150 children was followed for 69 years. Model inputs were derived from the literature, with an incremental cost-effectiveness ratio (ICER) willingness-to-pay threshold of $100,000/quality-adjusted life year (QALY) used to delineate cost effectiveness. Outcomes included prevalence of severe neurological morbidity (SNM), SCD, cost, and QALYs. In children at intermediate risk of SCD (4–6% over 5 years), ICD resulted in 56 fewer cases of SNM, 2686 fewer deaths. In children at high risk (> 6% over 5 years), ICD placement resulted in 74 fewer cases of SNM and 3663 fewer deaths from cardiac causes. The costs of ICD were higher, but placement was cost effective with an ICER of $3009 per QALY in intermediate risk children, but ICD therapy was a dominant strategy in high-risk children. Sensitivity analysis demonstrated ICD placement was cost-effective until the annual probability of SCD was < 0.22%. The model was robust over a wide range of values. For children at risk of SCD, prophylactic ICD implantation is cost effective, resulting in improved outcomes and increased QALYs, despite increased costs. These findings highlight the economic benefits of ICD utilization in this population.