Objective: This study aimed to evaluate whether the A, B and 0 blood groups (AB0) subgroup distribution of patients with idiopathic granulomatous mastitis (IGM) is different or notdiffers from that of the general population. Methods: The patients with IGM who were followed up in the breast unit and applied for routine control between July 2021 and October 2021 were included in the study. Results: During this period, 101 IGM patients were enrolled. The patients’ age ranged between 21 and 61 years (median, 33 years). The most common AB0 blood subgroup in both the patient and control groups was Group A (48.5% and 44.7%, respectively). Between the groups, the difference in AB0 subgroups was not statistically significant (p=0.122). Eight patients had erythema nodosum. In 75% of patients with erythema nodosum, the most common AB0 subgroup was Group A. Eight patients developed relapses. The AB0 subgroup was A in five of the patients who had a relapse. However, the comparison of AB0 subgroups according to both erythema nodosum and relapse status could not be performed because there were few such cases, and the data did not satisfy the necessary assumptions for the chi-square test. Conclusion: In our study, the AB0 blood group distributions in both patient and control groups were similar, and our data did not support a relationship between IGM and AB0 blood groups.