Background: Patients undergoing implantable cardioverter-defibrillator (ICD) implantations have high rates of long-term device-related complications and reoperations. Whether physician specialty training is associated with differences in long-term outcomes following ICD implantation is unclear. Methods and Results: We linked data from the National Cardiovascular Data Registry ICD Registry with Medicare fee-for-service claims to identify physicians who performed ≥10 index ICDs from 2006 to 2009. We used data from the American Board of Medical Specialties to group the specialty of the implanting physician into mutually exclusive categories: electrophysiologists, interventional cardiologists, general cardiologists, thoracic surgeons, and other specialties. Primary outcomes were long-term device-related complications requiring reoperations or hospitalizations and reoperations for reasons other than complications. We compared the cumulative incidence rates and case-mix adjusted rates of long-term outcomes of index ICD implantations across physician specialties. Our analysis had a median follow-up of 47 months and included 107 966 index ICD implantations. Electrophysiologists had the lowest rates of incident long-term device-related complications (14.1%; interventional cardiologists, 15.3%; general cardiologists, 15.4%; thoracic surgeons, 16.4%; other specialists, 15.2%; P <0.001) and reoperations for reasons other than complications (electrophysiologists, 16.7%; interventional cardiologists, 17.0%; general cardiologists, 18.0%; thoracic surgeons, 18.4%; other specialists, 18.0%; P <0.001). Compared with patients whose ICDs were implanted by electrophysiologists, patients with implantations performed by nonelectrophysiologists were at higher risk of having long-term device-related complications (relative risk for interventional cardiologists: 1.16 [95% CI, 1.08–1.25]; general cardiologists: 1.13 [1.08–1.18]; thoracic surgeons: 1.20 [1.06–1.37]; all P <0.001, but not other specialists: 1.08 [0.99–1.17]; P =0.07). Compared to patients with implantations performed by electrophysiologists, patients with implantations performed by general cardiologists and thoracic surgeons were at higher risk of reoperation for noncomplication causes (relative risk for general cardiologists: 1.10 [1.05–1.15]; thoracic surgeons: 1.16 [1.00–1.33]; both P <0.05). Conclusions: Patients with ICD implantations performed by electrophysiologists had the lowest risks of having long-term device-related complications and reoperations for noncomplication causes. Consideration of physician specialty before ICD implantation may represent an opportunity to minimize long-term adverse outcomes.