LncRNA MCM3AP-AS1 has been reported to be upregulated and plays an oncogenic role in papillary thyroid cancer. However, analysis of the Cancer Genome Atlas (TCGA) dataset revealed MCM3AP-AS1 downregulation in cervical squamous cell carcinoma (CSCC). This observation encouraged us to analyze the function of MCM3AP-AS1 in CSCC. The research subjects of the present study were 62 CSCC patients (42 to 68 years; 53.7 ± 6.8 years). Based on medical records, there were 51 HPV-positive cases of and 11 HPV-negative cases. Gene expression was analyzed by RT-qPCR. The interactions among MCM3AP-AS1, miR-21, and PTEN were explored by overexpression assays followed by RT-qPCR and Western blot. CCK-8 cell proliferation analysis and cell apoptosis analysis were applied to study the roles of MCM3AP-AS1, miR-21, and PTEN in regulating cell proliferation and apoptosis in CSCC. We found that MC-M3AP-AS1 was downregulated in CSCC patients, and its low level was closely correlated with patients' poor survival. MCM3AP-AS1 could directly interact with miR-21. However, miR-21 overexpression failed to affect MCM3AP-AS1 expression. Interestingly, MCM3AP-AS1 overexpression decreased the expression of PTEN, which is a target of miR-21. Cell proliferation and apoptosis analysis showed that MCM3AP-AS1 and PTEN overexpression increased apoptosis but decreased proliferation of CSCC cells. MiR-21 overexpression played an opposite role and attenuated the effects of MCM3AP-AS1 overexpression. Therefore, MCM3AP-AS1 may regulate the miR-21/PTEN axis to regulate CSCC cell proliferation and apoptosis.