Objective: The aim of the idiopathic granulomatous mastitis (IGM) consensus study was to evaluate the etiology, diagnostic steps, and differential diagnosis and propose a widely accepted clinical classification of this mysterious breast disease. Method: The organization of a national IGM consensus was decided by the joint evaluation of the Turkish Federation of Breast Diseases Societies, SENATURK, and the Society of Breast Surgery. First, a working group of 11 members was formed, and a survey and workshop were organized to reach a common consensus. The modified Delphi method was used in the consensus methodology. Voting rates of 80% and above were considered as acceptance. Results: The consensus was 45/50 (92%) that core needle biopsies are necessary for the diagnosis of IGM and 39/40 (97%) that a new clinical classification is needed. The proposed Turkish clinical classification of IGM was accepted by 94% in three rounds of voting. Conclusion: This disease should be considered etiologically idiopathic. Tissue diagnosis and pathological evaluation are recommended for treatment. The proposed IGM Turkey classification was strongly accepted.