Purpose To evaluate the effectiveness of treatment with topical and intralesional steroids for idiopathic granulomatous mastitis (IGM) and to compare with surgical methods. Methods Data were retrospectively collected from records. Intralesional steroid injection and topical steroid administration, hereafter referred to as local steroid treatment (LST) were applied in Group 1. Surgery (local excision, wide excision, and mastectomy) was performed in Group 2. In Group 1, changes in lesion sizes were recorded and factors complicating treatment were identified. The Numeric Pain Rating Scale was used to determine subjective pain. LST and surgery were compared with regard to: pain before and after the treatment; complication rate; recurrence rate; and treatment cost. Results There were 38 and 48 patients in Group 1 and Group 2, respectively. In the LST group, 72 lesions were present and 70 of 72 (97%) responded completely to treatment. Pretreatment median maximum diameter was 23.50 (15.25-35.25) mm, which regressed to 16 (12-25) mm after the first session. While the pretreatment pain scores of Group 1 and Group 2 were similar (p = 0.756), there was a significant difference in the post-treatment pain scores (p < 0.001). No recurrence occurred in any patients in Group 1, while recurrence developed in 15 (31.2%) patients in Group 2 (p < 0.001). Conclusion LST is a treatment for IGM that is cheap, with high efficiency, negligible recurrence, and has good esthetic outcome. Our results suggest that LST should be the first-line treatment option for all IGM patients, including complicated cases.