We report a case of bilateral breast cancer lesions treated successfully by partial oncoplastic surgery. A 46-year-old Japanese woman presented with a small mass in the right breast. Mammography showed neither a mass nor calcification in the right breast; however, an irregular-shaped mass lesion was shown in the left breast. Ultrasonography and fine-needle aspiration biopsy revealed ductal carcinoma in situ in the inner-upper quadrant of the right breast and invasive ductal carcinoma in the outer-upper quadrant of the left breast. We considered that it would be difficult to obtain a good symmetrical outcome after partial mastectomy for the bilateral breast lesions because of the asymmetrical location of each lesion and her ptotic breasts. Thus, we performed bilateral partial resection, followed by an inferior pedicle reduction mammaplasty-type operation, with and without axillary lymphadenectomy, and achieved good cosmetic and oncologic results.