We report a case of pelvic metastasis of rectal cancer that developed 10 years after curative resection. An 81-year-old woman underwent intersphincteric resection for lower rectal cancer 10 years previously. The tumor was pathologically diagnosed as T2N0M0, Stage Ⅰ. Nine years after the curative resection, serum carcinoembryonic antigen(CEA)levels were slightly elevated, but no recurrence was found on computed tomography(CT). Eleven months after CT, serum CEA levels elevated to 15.9 ng/mL. Pelvic metastasis in the piriformis muscle was detected on positron emission tomography(PET)-CT. Following CT-guided biopsy, she was pathologically diagnosed with metastatic rectal cancer. Radiotherapy (60 Gy/30 Fractions) was administered. Ten months after radiotherapy, PET-CT revealed no relapse in the pelvis with lung metastases.