Background - Percutaneous coronary intervention (PCI) for stable coronary artery disease does not reduce the risk of death and myocardial infarction compared with optimal medical therapy (OMT), but many patients think otherwise. PCI Choice, a decision aid (DA), was designed for use during the clinical visit and includes information on quality of life and mortality outcomes for PCI with OMT versus OMT alone for stable coronary artery disease. Methods and Results - We conducted a randomized trial to assess the impact of the PCI Choice DA compared with usual care when there is a choice between PCI and optimal medical therapy. Primary outcomes were patient knowledge and decisional conflict, and the secondary outcome was an objective measure of shared decision making. A total of 124 patients were eligible for final analysis. Knowledge was higher among patients receiving the DA compared with usual care (60% DA; 40% usual care; P=0.034), and patients felt more informed (P=0.043). Other measures of decisional quality were not improved, and engagement of the patient by the clinician in shared decision making did not change with use of the DA. There was evidence that clinicians used the DA as an educational tool. Conclusions - The PCI Choice DA improved patient knowledge but did not significantly impact decisional quality. Further work is needed to effectively address clinician knowledge gaps in shared decision-making skills, even in the context of carefully designed DAs. Clinical Trial Registration - URL: https://www.clinicaltrials.gov/. Unique identifier: NCT01771536.