Purpose To investigate the effects of intra-articular glenohumeral joint triamcinolone injection in treating secondary adhesive capsulitis after breast cancer surgery.Methods This study prospectively enrolled 37 participants, 22 of the breast cancer surgery group and 15 of the idiopathic group. All participants received intra-articular glenohumeral joint injection in the affected shoulder joint and received physiotherapy for 12 week. The clinical assessment evaluated before, and 1, 3, and 6 months after the intervention. The primary outcome was the change in the Shoulder Pain and Disability Index (SPADI).Results The total SPADI(%) in both groups showed significant decrease from baseline to 1, 3, and 6 months after the intervention. There was no significant difference in the differences of the total SPADI from baseline to 1, 3, and 6 months between two groups. However, the improvement in the SPADI pain subscale and the PROM of abduction at 3 and 6 months post-injection in the breast cancer group were inferior to the idiopathic group.Conclusion Intra-articular triamcinolone injection for adhesive capsulitis after breast cancer surgery significantly improved in significant improvements of pain, shoulder function and the PROM. The effects were similar to idiopathic adhesive capsulitis, but in the breast cancer surgery group, appropriate pain and ROM management and monitoring are required even 3 months after injection. With a standardized injection protocol, intra-articular triamcinolone injection could be an effective and safe treatment option for secondary adhesive capsulitis after breast cancer surgery.