This randomized controlled trial aimed to compare the short-term effectiveness of high-intensity laser therapy (HILT) and a multimodal physiotherapy program in patients with subacromial impingement syndrome (SIS). Ninety-four participants were allocated to either HILT or combined physiotherapy, and both groups received an identical supervised exercise program. Primary outcome measures included shoulder pain assessed using the visual analogue scale (VAS). Secondary outcomes included shoulder function, disability, and quality of life. Outcomes were evaluated at baseline, post-treatment, and short-term follow-up.