Background and objectives: The aim of this study is to investigate the effect of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) in idiopathic granulomatous mastitis (IGM). Methods: This case-control study was conducted in Saglik Bilimleri and Necmettin Erbakan Universities. Sixty patients with IGM diagnosis (Group P) and 25 healthy females as control group (Group C) were included. Group P was divided into two subgroups according to the activity of disease: patients with active lesion (Group PA), and patients without any symptoms, in remission (Group PR). The ELISA method was used to measure sTREM-1 level. Results: Group P’s sTREM-1 were higher than Group C (p < .0001). The difference between sTREM-1 levels of Groups PA, PR and C was significant statistically (p < .0001). Group PA’s sTREM-1 levels were higher than Group C (p < .0001). Also, sTREM-1 levels of Group PR were higher than Group C (p = .006). When sTREM-1 levels of patients receiving steroid therapy and did not in Group PR were analyzed, the sTREM-1 levels of the patients not receiving steroid treatment were found to be statistically higher than Group C (p = .002). Although the sTREM-1 levels of the patients who did not receive steroid therapy were higher than those who received steroid therapy, the difference was not statistically significant (p > .05). Conclusion: We concluded that the detected high sTREM-1 levels contributed to inflammation in IGM. In particular, blockade of TREM may be a promising treatment option in resistant or multiple recurrent patients.