There are few reports that describe the efficacy of proton beam therapy for lymph node metastasis of recurrent rectal cancer, and carbon ion radiotherapy yields higher local tumor control rates. Proton beam therapy needs a longer treatment period but is less toxic to adjacent healthy organs compared to carbon ion radiotherapy. Here we report an 85-year-old man who underwent curative surgery for rectal and sigmoid cancer at the age of 76 years. After 4 years and 2 months, he had liver metastases at S3 and S8, both of which were resected. Eight years and 6 months after primary resection, CT imaging revealed a solitary lymph node metastasis of 28mm in the minor axis, adjacent to the portal vein and IVC. Because of the location and patient's age, proton beam therapy was selected as the treatment strategy, rather than surgery or chemotherapy. A total of 67.5 GyE/25 fx proton beam therapy was applied. CT imaging 4months after irradiation revealed a partial response(PR)and the tumor had shrunk to 8mm. PR continued for 2 years and 1 month. Although the tumor relapsed after 3 years of irradiation and had grown to 16 mm, the patient had no adverse events or symptoms throughout this period. Proton beam therapy may be one of the options for tumors at difficult locations in fragile patients because of its reduced toxicity.