Background: This study investigated the clinical effectiveness of Korean medicine (KM) treatment for shoulder impingement syndrome (SIS). Methods: There were 61 patients who were diagnosed with SIS in the Jaseng hospital network of KM (7 hospitals located in Korea: Gangnam, Daejeon, Bucheon, Haeundae, Bundang, Ulsan, and Gwangju) between January 1st, 2015 and December 31st, 2020 who were retrospectively reviewed. The patients were grouped according to complications, intake of analgesics, duration of illness preadmission, and treatment. Treatments consisted of herbal medicine, acupuncture, cupping, Chuna, pharmacopuncture, bee venom pharmacopuncture, medicinal steaming, Daoyin exercises, and physical therapy. By comparing the Numeric Rating Scale (NRS), Shoulder Pain and Disability Index, and European Quality of Life 5-Dimensions questionnaire scores, the effectiveness of integrated KM treatment was evaluated. Results: There were 14 males and 47 females. For inpatients diagnosed with SIS, the mean NRS score decreased from 5.78 ± 1.33 to 3.40 ± 1.43 (p < 0.001). The mean Shoulder Pain and Disability Index score decreased from 53.87 ± 14.76 to 38.56 ± 18.87 (p < 0.001), and the mean European Quality of Life 5-Dimensions questionnaire increased from 0.67 ± 0.13 to 0.76 ± 0.09 (p < 0.001) after KM treatment. Medicinal steaming (0.398; p < 0.001), acupuncture (0.290), cupping (0.288), bee venom pharmacopuncture (0.282), and Daoyin exercises (0.262; p < 0.05) had a positive correlation with improved changes in the NRS score. Conclusion: Conclusion: Treatment with integrated KM treatment improved the pain, range of motion, shoulder function, and quality of life of patients with SIS.