Importance: Recent evidence has suggested that skeletonization of the internal thoracic artery (ITA) is associated with worse clinical outcomes in patients undergoing coronary artery bypass surgery (CABG). Objective: To compare the long-term clinical outcomes of skeletonized and pedicled ITA for CABG. Design, Setting, and Participants: The Arterial Revascularization Trial (ART) was a 2-group, multicenter trial comparing the use of a bilateral ITA vs a single ITA for CABG at 10 years. Patients in the ART trial were stratified by ITA harvesting technique: skeletonized vs pedicled. Data were collected from June 2004 to December 2017, and data were analyzed from June to July 2021. Interventions: In this analysis, the 10-year clinical outcomes were compared between patients who received skeletonized vs pedicled ITAs. Main Outcomes and Measures: The primary outcome was all-cause mortality. The secondary outcomes were a composite of major adverse cardiac events (MACE) including all-cause mortality, myocardial infarction, and repeated revascularization and a composite including MACE and sternal wound complication (SWC). Cox regression and propensity score matching were used. Results: Of 2161 included patients, 295 (13.7%) were female, and the median (interquartile range) age was 65.0 (58.0-70.0) years. At 10 years, the risk of all-cause mortality was not significantly different between the pedicled and skeletonized groups (hazard ratio [HR], 1.12; 95% CI, 0.92-1.36; P =.27). However, the long-term risks of the secondary outcomes were significantly higher in the skeletonized group compared with the pedicled group (MACE: HR, 1.25; 95% CI, 1.06-1.47; P =.01; MACE and SWC: HR, 1.22; 95% CI, 1.05-1.43; P =.01). The difference was not seen when considering only patients operated on by surgeons who enrolled 51 patients or more in the trial (MACE: HR, 1.07; 95% CI, 0.82-1.39; P =.62; MACE and SWC: HR, 1.04; 95% CI, 0.80-1.34; P =.78). Conclusions and Relevance: While the long-term survival of patients was not different between groups, the rate of adverse cardiovascular events was consistently higher in the skeletonized group and the difference was associated with surgeon-related factors. Further evidence on the outcome of skeletonized ITA is needed.