BACKGROUND Metachronous ovarian metastasis from primary colorectal cancer (CRC) is a rare condition that is diagnosed after the treatment of CRC. In most cases, ovarian metastases present without specific symptoms or signs and are usually diagnosed during follow-up imaging. A rare case is presented of metachronous ovarian metastasis from primary CRC, diagnosed on follow-up by computed tomography (CT) and magnetic resonance imaging (MRI), and includes a review of the literature. CASE REPORT A 66-year-old woman recently underwent a left hemicolectomy for a stage T3, N0, M0 primary adenocarcinoma of the sigmoid colon, which was completely excised. Three years later, follow-up CT and MRI imaging showed a right ovarian cyst. She underwent exploratory laparotomy and bilateral salpingo-oophorectomy, which identified tumor in the right ovary. Histopathology and immunohistochemistry confirmed metachronous ovarian metastasis from CRC. The patient was referred for further treatment. CONCLUSIONS Newly-diagnosed ovarian metastasis from primary colorectal cancer (CRC) is challenging to diagnose and manage, and may initially be incorrectly diagnosed as malignancy of primary ovarian origin. This case demonstrated that it is important to confirm the diagnosis with imaging, histology, and the appropriate use of tumor markers. Because ovarian metastases do not respond favorably to chemotherapy, the treatment of choice is surgery. However, for women who are treated for CRC, the use of prophylactic oophorectomy remains controversial.