Idiopathic granulomatous mastitis (IGM) is a benign chronic inflammatory breast disease of unknown etiology. No consensus exists as to the best therapeutic approach, though treatment choices include antibiotics, drainage, surgical excision, steroids, methotrexate, and observation. Herein we report a case of idiopathic granulomatous mastitis that was refractory to methotrexate and intralesional and systemic steroids but responded well to mycophenolate mofetil 1500mg twice daily. To our knowledge, this is the first report of the effective use of mycophenolate mofetil in idiopathic granulomatous mastitis.