A mucinous carcinoma of the breast is a well-differentiated rare histological type of invasive ductal carcinoma, having a lower frequency of metastasis to an axillary lymph node and a better survival rate. Bilateral breast cancer has an overall incidence of 4% to 20% in patients with primary operable breast cancer. Few reports exist in the clinical literature characterizing a synchronous bilateral mucinous carcinoma of the breast. We report the characteristic imaging findings of a bilateral mucinous carcinoma of the breast.