While Baduanjin, a traditional Chinese mind-body exercise, has shown potential health benefits, its efficacy in improving outcomes for heart failure patients with mildly reduced or preserved ejection fraction (HFmrEF/HFpEF) has not been well documented. We aimed to investigate the adjunctive impact of Baduanjin on exercise capacity and quality of life for HFmrEF/HFpEF. Patients with HFmrEF/HFpEF were enrolled in this multicenter randomized clinical trial. All participants were randomized to conventional cardiac rehabilitation with or without an additional 12-week Baduanjin exercise. The primary endpoint was the distance covered in a 6-min walk test (6MWD), while key secondary outcomes included quality of life measured by the Minnesota Living with Heart Failure Questionnaire (MLHFQ) and cardiopulmonary function including anaerobic threshold (VO2 AT). A total of 120 patients were enrolled, and 109 completed all session and tests. The mean age of the 120 patients was 60.5 years (SD, 9.21 years), and 23 (19.2%) were women. The Baduanjin group exhibited a 6.14% improvement in 6MWD compared to a 1.32% improvement in the control group (median improvement, 25.0vs. 5.0m; p<0.001) at 12th week. The VO2 AT increased by 25.87% in the Baduanjin group versus 3.94% in the control group (p<0.001). Quality of life also significantly improved in the Baduanjin group as indicated by MLHFQ score changes (-16.8% vs. -3.99%; p<0.001). Adding Baduanjin to exercise-based cardiac rehabilitation for patients with ischemic HFmrEF or HFpEF are generally safe and could provide significant improvements in exercise capacity and quality of life.