Idiopathic granulomatous mastitis (IGM) is a rare, benign inflammatory disorder of the breast. Clinical features may include painful breasts, erythema, subcutaneous nodules, and ulcerative lesions. It can mimic various other breast pathologies, and it is a diagnosis of exclusion after infection, malignancy, and other inflammatory conditions have been ruled out. In this article, we present a case of IGM developing in a 40-year-old female 3 months after hospitalization for myxedema coma. A contrast-enhanced magnetic resonance imaging of the breasts showed bilateral edema, and a biopsy was negative for malignancy or infection. She was started on prednisone and had noticeable improvement of ulcerations within several weeks. IGM is a rare condition that requires a multimodal treatment approach. Often recalcitrant disease is encountered and requires surgical intervention, immunosuppression, and antimicrobial therapy. The diagnosis should be entertained in patients with bilateral breast inflammation to avoid unnecessary surgical resection early on.