Objectives: To evaluate the 3 -month effects of pulsed electromagnetic field therapy (PEMF) in the treatment of subacromial impingement syndrome (SIS). Design: Planned analysis of a randomized controlled trial with 4- and 12 -week follow-ups. Setting: Physical medicine and rehabilitation clinic, treatment unit. Participants: Of the 250 individuals screened for eligibility, participants with a diagnosis of SIS (N=80) were randomized to intervention or control groups. Intervention: The first group received PEMF + exercise and the second group received sham PEMF + exercise 5 days a week for a total of 20 sessions. Main Outcome Measures: Visual Analog Scale (VAS), Constant Murley Score (CMS), Shoulder Pain and Disability Index (SPADI), Short Form36 (SF -36) Quality of Life Questionnaire, and shoulder muscle strength measurement with an isokinetic dynamometer. Evaluations were performed before treatment (T0), after treatment (T1), and 12th week (T2). Results: Evaluation at T1 and T2 showed improvement in most parameters in both groups compared with baseline. In the comparison between the 2 groups at T1 and T2, more improvement was found in the PEMF group in most parameters. Conclusions: In our study, PEMF was found to be superior to sham PEMF in terms of pain, ROM, functionality, and quality of life at the first and third months.