We describe clinicopathologic and immunohistochemical features of an unusual case of cystic fibrosis manifesting in the cervix as a mass lesion, mimicking cervical adenocarcinoma. A 24-year-old nulligravida with cystic fibrosis developed heavy postcoital vaginal bleeding 4 months after starting oral contraceptives and was found to have a cervical mass. She underwent a loop electrosurgical excision of the mass, and microscopic examination revealed a florid endocervical proliferation, extending to the margins. This lesion was initially interpreted as an invasive, well-differentiated endocervical adenocarcinoma. However, on subsequent review, the lesion was found to have a low rate of proliferation, no evidence of an infiltrative growth pattern, and abundant acute inflammation. Given these findings and the absence of any residual endocervical lesion on a subsequent cold knife conization, we determined that this was a benign, likely reactive, lesion. This case, together with previous studies, suggests that women with cystic fibrosis can develop proliferative endocervical lesions and that oral contraceptives may contribute to their development.