We report a case of locally advanced rectal cancer, treated effectively with chemotherapy consisting of mFOLFOX6 combined with radiotherapy. A 63-year-old man was admitted to our hospital in March 2012 for diarrhea and anal and perineal pain. Advanced rectal cancer with invasion ofthe right perineum was diagnosed based on computer tomography(CT) findings. Surgery was performed; however, the rectal cancer was unresectable. A sigmoid colostomy was performed, and a central venous port was implanted. In April 2012, the patient was treated with chemotherapy using 3 courses ofmFOLFOX6 and concurrent radiotherapy. Radiotherapy at 2 Gy/day was administered 25 times(total dose, 50 Gy). After chemoradiotherapy, the patient underwent 3 courses ofmFOLFOX6 as an additional therapy. By June 2012, CT showed resolution ofthe tumor in the right perineum and a marked decrease in the size ofthe primary rectal cancer. Because the patient refused surgery, we started treatment with combination chemotherapy using oral S-1 and intravenous CPT-11 in August 2012. After 18 courses, the treatment was changed to oral administration ofS -1 alone, which was continued for 1 year. The patient remained well without recurrence for 54 months since the original diagnosis. Therefore, chemoradiotherapy with mFOLFOX6 is a possible option for the management of advanced rectal cancer.