Objective: To investigate if adding Kinesio tape to therapeutic exercise is an effective treatment to improve clinical outcomes compared to therapeutic exercise alone and no intervention, in patients with shoulder impingement syndrome. Design: Three-arm randomized controlled trial Setting: Outpatient setting Subjects: One hundred and twenty patients (mean (SD): age 37.8 (5.4)) with shoulder impingement syndrome. Intervention: Patients were randomly assigned to eight-weeks therapeutic exercise alone, therapeutic exercise with Kinesio tape, and control group. Main measures: Pain was measured with a numerical rating scale and disability and scapular kinematics were measured with a relative questionnaire and motion analysis software respectively, at baseline and after eight-weeks intervention. Results: There was significant differences in therapeutic exercise with Kinesio tape group vs. therapeutic exercise alone and control group respectively for pain ( d = –0.34, P = 0.042; and d = –1.53, P = 0.001), disability ( d = –0.46, P = 0.024; and d = –2.18, P = 0.001), scapular upward rotation at sagittal plane ( d = 0.33, P = 0.033; and d = 0.68, P = 0.001), scapular plane ( d = 0.18, P = 0.045; and d = 0.43, P = 0.001), scapular tilt at sagittal plane ( d = 0.55, P = 0.043; and d = 1.39, P = 0.001), and scapular plane ( d = 0.29, P = 0.034; and d = 0.58, P = 0.001). Therapeutic exercise alone was superior over control group in all significant outcomes ( P < 0.05). Conclusion: Although therapeutic exercises alone showed positive effect on clinical outcomes, adding Kinesio tape to therapeutic exercises had more significant effects with larger effect sizes. Adding Kinesio tape to therapeutic exercise may be of some assistance to clinicians in improving clinical outcomes in patients with shoulder impingement syndrome.