BACKGROUND: Individuals with shoulder pain have a higher occurrence of myofascial trigger points (MTrPs). In the past decade, dry needling (DN) has been used in physical therapy practice to treat MTrPs. Impaired blood flow is proposed as an underlying mechanism of MTrPs in neck-shoulder pain. However, whether DN would improve muscle blood flow in individuals with shoulder pathology has not been examined. Therefore, the primary purpose of this study was to use color Doppler imaging to examine the effects of DN on the blood flow of the infraspinatus muscle in individuals with shoulder pain. The secondary purpose was to examine the effects of DN on sensitivity to pressure and shoulder range of motion (ROM) of the infraspinatus muscle in individuals with shoulder pain. METHOD: This randomized comparison trial utilized a sham-controlled design. Forty individuals with nonspecific shoulder pain and at least one MTrP in the infraspinatus muscle were randomly assigned to a real DN group or a sham DN group. Outcome measures, including blood flow parameters, ROMs of shoulder internal rotation and external rotation, and pressure pain threshold (PPT) were collected before and immediately after a single session of DN. RESULTS: The repeated measure ANOVA results revealed that real DN significantly decreased peak systolic velocity (PSV) and increased shoulder internal and external rotation ROM more than sham DN ( CONCLUSION: The results indicated that participants who received real DN exhibited a significant reduction in PSV, suggesting improved blood flow to the infraspinatus muscle. Participants who received real DN exhibited improvements in shoulder ROM but showed no reductions in sensitivity to pressure. These results may provide clinicians with evidence for the use of DN for individuals with shoulder pain.