Introduction: The aim of the study was to evaluate the influence of estradiol-producing ovarian tumors, including surface epithelial-stromal tumors, on the cervical cytology of postmenopausal women. Methods: This case-controlled study included 160 postmenopausal women who underwent a gynecological surgery between January 2009 and December 2016. The relationship between serum estradiol levels and the maturation index of cervical cytology was examined. Patients with ovarian tumors and a high estradiol level (≥28 pg/mL) constituted the estradiol-producing ovarian tumor group (30 women, including 23 with surface epithelial-stromal tumors). The maturation index of this group was compared with that of the control group (130 women with normal estradiol levels [<28 pg/mL] with either ovarian tumors or uterine tumors). Results: For all patients, the serum estradiol levels were significantly correlated with the maturation index (p < 0.001, r = 0.65). The maturation index of the estradiol-producing ovarian tumor group was significantly higher than that of the control group (0.67 ± 0.21 vs. 0.075 ± 0.16, p < 0.001). The area under the receiver operating characteristic curve for the maturation index was 0.94. The best maturation index cut-off level for estradiol-producing ovarian tumors was 0.20. Using this cut-off, the sensitivity and specificity were 94% and 82%, respectively. Conclusion: Estradiol-producing ovarian tumors influence cervical epithelial maturation in postmenopausal women. An increased maturation index may trigger the early detection of asymptomatic ovarian tumors.