Forty-two patients with Subacromial Impingement Syndrome (SAIS) were randomized to High-Intensity Laser Therapy (HILT) +exercises (n=14), Low-level laser therapy (LLLT) + exercises (n=14), or exercises alone (n=14). The primary outcome was change in the Shoulder Pain and Disability Index (SPADI). Secondary outcomes included shoulder range of motion (goniometer), pain pressure threshold (algometer), and sleep quality (Pittsburgh Sleep Quality Index). Outcomes were assessed at baseline and after three weeks (nine sessions). Overall, the results revealed larger improvements with HILT versus LLLT and control for SPADI (pain, disability, total), PPT, and PSQI, with large effect sizes favoring HILT; ROM improved within all groups without consistent between-group differences. These findings suggest HILT is a more effective adjunct to exercise than LLLT for short-term pain, disability, nociceptive sensitivity, and sleep in SAIS.