Objective. The aim of this study is to explore the expressions and clinical significance of melanoma-associated antigen-A9 (MAGE-A9) in cervical cancer tissues and peripheral blood mononuclear cells (PBMC). Methods. 108 patients who were scheduled to undergo cervical conization or extensive hysterectomy between March 2019 and January 2021 due to cervical lesions were selected by convenient sampling. According to postoperative pathological results, the patients were divided into a cervical cancer group (n = 64) and cervical intraepithelial neoplasia (CIN) group (n = 44). The expression levels of MAGE-A9 mRNA in cervical lesion tissues and PBMC were detected by real-time fluorescence quantitative PCR, and the expression of MAGE-A9 protein in lesion tissues was detected by immunohistochemistry. The correlation between MAGE-A9 mRNA expressions in cancer tissues and PBMC and serum tumor markers in patients with cervical cancer and the relationship between MAGE-A9 protein expression in cancer tissues and clinicopathological characteristics were analyzed, and a receiver operating characteristic curve (ROC curve) was drawn to explore the diagnostic value of MAGE-A9 mRNA expressions in cancer tissues and PBMC on cervical cancer. Results. The expression levels of MAGE-A9 mRNA in cervical lesion tissues and PBMC in the cervical cancer group were significantly higher than those in the CIN group (P < 0.05), and the levels of serum SCC-Ag, CA-125, and CEA were significantly higher than those in the CIN group (P < 0.05). The positive rate of the MAGE-A9 protein expression in cervical lesion tissues in the cervical cancer group was significantly higher than that in the CIN group (P < 0.05). The expression levels of MAGE-A9 mRNA in cancer tissues and PBMC of patients with cervical cancer were positively correlated with serum SCC-Ag, CA-125, and CEA (P < 0.05). The positive rate of the MAGE-A9 protein expression in cervical cancer tissues was related to FIGO stage, tumor diameter, degree of differentiation, lymph node metastasis, and high-risk HPV infection (P < 0.05) and was not correlated with age and pathological type (P > 0.05). The areas under the ROC curves of MAGE-A9 mRNA in lesion tissue and MAGE-A9 mRNA in PBMC were 0.925 and 0.900 in the diagnosis of cervical cancer (P < 0.05). Conclusion. The expressions of MAGE-A9 in cancer tissues and PBMC of patients with cervical cancer are upregulated, which is related to the levels of serum tumor markers and the progression of disease. MAGE-A9 is expected to become an important marker for the diagnosis of early cervical cancer.