Clinical Scenario: Shoulder pain is the third most common musculoskeletal complaint. The most common type of shoulder pain is subacromial impingement syndrome (SIS). The concept of regional interdependence demonstrates that body regions are interrelated, affecting how they function. Previous studies have reported the influence of the thoracic spine on the shoulder. Clinical Question: Does adding thoracic spine manipulation or mobilization to exercise in adults with SIS improve shoulder range of motion (ROM), pain, and disability? Summary of Key Findings: The literature was searched for level 2 evidence or higher that examined the effects of the addition of thoracic mobilization or manipulation to exercises in shoulder ROM, pain, and disability in SIS. Twenty articles related to the clinical question, but only 3 met the inclusion and exclusion criteria. Two studies reported that the combination of thoracic mobilization or manipulation and exercises resulted in more significant improvements in shoulder ROM, pain, and disability compared to exercises alone. One study concluded that the combination of thoracic or shoulder mobilization to exercises was superior to ultrasound or exercises alone. Clinical Bottom Line: There is moderate evidence to support the addition of thoracic manipulation or mobilization to exercise in treating SIS to improve shoulder ROM, pain, and disability. Strength of Recommendation: Grade B evidence supports a multimodal approach using the combination of thoracic mobilization or manipulation and exercises in adults with SIS.