Endometriosis involving the uterine cervix is a rare condition that can lead to diagnostic errors in the interpretation of Pap smear. We report the case of a 41-year-old patient in whom the initial Pap smear revealed three-dimensional clusters of glandular cells with elongated nuclei, occasional mitosis, and atypia, which was interpreted as atypical glandular cells, not otherwise specified (NOS). The patient was taken to colposcopy and endocervical biopsy. Colposcopy was normal and the biopsy presented glands with elongated nuclei and surrounded by endometrial stroma admixed with normal endocervical glands. Immunohistochemical studies were reactive for CD10 in the stromal cells and vimentin in endometrioid glands. The findings were consistent with cervical endometriosis. Endometriosis in the cervix is an uncommon pathology that mimics malignancy and may be interpreted as atypical or glandular neoplasia in the cytology.