Purpose <p>Congenital heart disease (CHD) patients are at increased risk of developing infective endocarditis, particularly following placement of prosthetic valves, stents, and vascular conduits. As compared to studies of infective endocarditis in adults, there is limited data on use of FDG PET/CT for evaluation of pediatric CHD patients. The primary aim of this study is to determine the value of FDG PET/CT for detecting infective endocarditis in a cohort of pediatric and young adult patients with complex CHD, with a secondary aim of demonstrating the feasibility of obtaining adequate dietary preparation in these complex patients.</p> Methods <p>Single center retrospective review of patients undergoing ¹⁸F-FDG PET/CT for suspected endocarditis between April 2014 and October 2025. Patients were identified in a search of the radiology report database. The accuracy of FDG PET/CT was determined based on a combination of clinical outcomes, surgical findings, microbiology and pathology.</p> Results <p>67 patients accounted for the 75 examinations meeting inclusion criteria. Median age was 21 (IQR 15–26) years. The most common underlying diagnosis was Tetralogy of Fallot (<i>n</i> = 27). Implanted devices were present in 62/67 patients; 53/67 patients had more than 1 implanted device. RV/PA conduit (<i>n</i> = 48) and Melody valve (<i>n</i> = 27) were the most common implants. 50 of 75 (67%) examinations were positive by FDG PET/CT criteria. Sensitivity was 95.9%; specificity was 88.5%, with an overall accuracy of 93.3%. 73% of examinations had adequate suppression of myocardial FDG uptake.</p> Conclusions <p>¹⁸F-FDG PET/CT is sensitive and accurate for detecting infective endocarditis in the CHD population. With proper instruction, adequate dietary preparation can be successfully accomplished in pediatric patients of varying ages and co-morbidities.</p>