Our aim was to evaluate the effectiveness of dry needling (DN) combined with conventional physiotherapy in the recovery of patients with subacromial syndrome (SAS). A search was made of the main open access health science databases. The publication date was not limited for systematic reviews but was for randomized clinical trials (RCTs), which were limited to the last five years (from 2016) in English or in Spanish. Ninety-four studies were selected. In order to assess the quality of the studies, the JADAD scale or Oxford quality scoring system was used. A total of 402 patients were analyzed in all the studies in which the application of conventional physiotherapy was compared to the DN, either in a combination or in isolation. Improvements were obtained in pain intensity (Visual Analogic Scale VAS), Range of Movement (ROM), Pressure Pain Threshold (PPT), functionality with Disabilities of the Arm, Shoulder and Hand (DASH) and the Shoulder Pain and Disability Index (SPADI), and in the cost-benefit ratio. DN is effective and safe in reducing the pain and disability produced by SAS, with the best combination of treatment turning out to be conventional physiotherapy together with DN, obtaining more stable and longer-lasting benefits than merely applying the techniques in isolation.