© 2022 Wiley Periodicals LLCBackground: Shoulder impairment on the implant side is common after cardiac implantable electronic device (CIED) implantation. The aim of this study was to compare the efficacy and safety of the pendulum exercise (PE) and stretching and strengthening exercises (SSE) in preventing postimplantation shoulder impairment. Methods: This prospective, randomized study collected data from 89 patients, including 30 in a control group, 31 in a PE group, and 28 in an SSE group. Shoulder functions on the implant side were evaluated by grip strength (GS), range of motion (ROM), Visual Analog Scale (VAS), Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH), and 36-Item Short-Form Survey (SF-36). Results: Shoulder median flexion and abduction ROM were significantly improved 2-month postimplantation compared to two-week postimplantation in PE (156 ± 11 vs. 146 ± 10, p =.002; 147 ± 9 vs. 136 ± 9, p =.001, respectively) and SSE (158 ± 13 vs. 147 ± 11, p =.003; 149 ± 13 vs. 138 ± 9, p =.002, respectively) groups, but not in the control group. Two months after implantation, the two exercise groups showed no significant differences in any assessment. Compared with the PE and SSE groups, the control group had significantly lower GS (p =.012 and p =.002, respectively) and SF-36 physical component summary (p =.007 and p =.003, respectively) and significantly higher VAS (p =.003 and p =.001, respectively) and QuickDASH (p =.002 and p =.005, respectively) scores 2-month postimplantation. Conclusions: PE and SSE for the ipsilateral upper arm starting two-week after CIED implantation provided similar benefits in preserving shoulder girdle muscle strength, maintaining shoulder motion, relieving shoulder pain, preventing shoulder injury, and improving quality of life, without the risk of lead dislodgement.