Background: Besides the traditional physical therapy interventions (infrared and strengthening exercises for scapular and shoulder muscles), recently, low-level laser (LLL) and mobilization with movement (MMM) gained more attention in the management of shoulder impingement syndrome (SIS). Aim: To examine the effects of adding LLL to MMM in patients having SIS. Design: A prospective double-blinded randomized trial. Settings: Physical therapy outpatient clinic of Heliopolis University. Participants: Forty patients complaining of unilateral shoulder impingement syndrome for not less than three months and not more than twenty-four months were included. Methods: The patients were randomly assigned to group A (n=20, received the active LLL, MMM, and the above-mentioned traditional physical therapy interventions), and group B (n=20, received the same treatments as group A but the LLL was sham). All treatments were applied 3 times per week, for 6 successive weeks. The shoulder pain severity, (assessed via visual analog scale, VAS) and shoulder range of motion (ROM) (flexion, abduction, and internal rotation). Results: The within-group analysis revealed a significant enhancement in all parameters relative to the baseline (P < 0.05). Conclusion: LLL could magnify the gained improvements in pain and ROM when added to MMM and traditional physical therapy interventions in patients with SIS.