The relapses of rectal cancer are most frequently localized in the pelvis, liver, and pelvic and para-aortic lymph nodes and lungs, whereas the vagina is an unusual site. We present here a 60-year-old woman presenting with lower abdominal discomfort 23 months after radical resection of rectal adenocarcinoma. An isolated, solitary, hypermetabolic mass in the right part of the vagina was detected by F-FDG PET/CT. Ultimately, the vaginal neoplasm was proved to be adenocarcinoma of rectal origin based on its shared histologic features and compatible immunostaining profile.