Background: Vaginal metastasis from organs other than the uterus is rare. Generally, patients with vaginal metastasis from colorectal cancer have a dismal prognosis. Although biopsy is the best method to make the diagnosis, massive bleeding may occur. On the other hand, liquid-based cytology (LBC) has the utility to perform immunocytochemistry on additional unstained slides: we can make a diagnosis with several immunocytochemical findings. Case: A 67-year-old postmenopausal female presented to our hospital with vaginal bleeding. The patient had undergone colectomy because of her stage III sigmoid colon cancer 3 years earlier. The patient had also undergone hysterectomy for cervical cancer 30 years earlier. LBC from the vaginal stump revealed adenocarcinoma. Immunocytochemically, cancer cells were negative for cytokeratin 7 and positive for cytokeratin 20, which suggested metastasis from the sigmoid colon cancer; the diagnosis was made without a biopsy. Conclusion: When the patient has a metastatic lesion from colon adenocarcinoma, LBC with immunocytochemistry is useful in making a diagnosis.