Glenohumeral osteoarthritis is a major cause of progressive shoulder pain and functional impairment. This systematic review and meta-analysis evaluated the effectiveness of intra-articular hyaluronic acid (IAHA) injections in reducing pain in shoulder osteoarthritis. A literature search of PubMed, Scopus, and Web of Science identified randomized controlled trials (RCTs) reporting post-intervention pain outcomes. A total of 15 studies involving 1,023 participants were analyzed. The results showed that the combination of IAHA and physiotherapy provided greater pain improvement than physiotherapy alone, and that IAHA was more effective than corticosteroid injections based on visual analog scale (VAS) scores. In addition, one study reported that a single injection of non-animal hyaluronic acid (NASHA) resulted in clinically and statistically significant pain reduction. These findings support IAHA as an effective non-surgical treatment option for shoulder osteoarthritis.