Background: Recent international studies have demonstrated that vaginal microbiota dysbiosis is associated with persistent human papillomavirus (HPV) infection, cervical precancerous lesions, and cervical cancer. In healthy women, Lactobacillus spp. dominate the vaginal microbiota and produce lactic acid and other bioactive compounds, thereby maintaining an acidic vaginal pH and protecting against colonization by pathogenic microorganisms. A reduction in Lactobacillus spp. and overgrowth of pathogenic bacteria, resulting in dysbiosis, has been associated with HPV persistence as well as the progression and recurrence of cervical precancerous lesions. However, no study has compared the prevalence of Lactobacillus spp. and aerobic bacteria, or their associations, among Mongolian women diagnosed with cervical precancerous lesions or cervical cancer. Therefore, this study was conducted to address this gap. Aim: To compare and characterize the composition of selected vaginal microorganisms in women diagnosed with cervical precancerous lesions and cervical cancer. Materials and Methods: This hospital-based, cross-sectional study was conducted from May to October 2026 at the Department of Gynecologic Oncology, National Cancer Center of Mongolia. A total of 275 women with histologically confirmed cervical precancerous lesions or cervical cancer were voluntarily enrolled after providing written informed consent. Prior to initiation, ethical approval was obtained from the Research Ethics Committee of the Mongolian National University of Medical Sciences at its meeting held on April 22, 2026 (Minutes No. 2026/04-28). General information, medical history, and behavioral factors were collected using a structured questionnaire. Three vaginal swabs were collected from the posterior vaginal fornix. Vaginal discharge was examined, and Lactobacillus spp. and aerobic bacteria were cultured. The associations between these microbiological findings and diagnostic groups were compared across five diagnostic categories. Results: Of the 275 women enrolled, the diagnostic distribution was as follows: CIN I, 41 (14.9%); CIN II, 73 (26.5%); CIN III, 80 (29.1%); cervical carcinoma in situ (CIS), 45 (16.4%); and cervical cancer (CC), 36 (13.1%). Vaginal pH was significantly and positively correlated with the cocci count (ρ=0.346, p < 0.001), white blood cell count (ρ=0.283, p < 0.001), and AV score (ρ=0.277, p < 0.001). In contrast, the Lactobacillus count was significantly and negatively correlated with vaginal pH (ρ=−0.238, p < 0.001). When the AV score was compared across diagnostic groups, it was 2.8±1.3 in stage IIB cervical cancer and 3.67±2.3 in stage III cervical cancer (p=0.008). Lactobacillus spp. were isolated from 119 participants (43.3%), while aerobic bacteria were isolated from 103 participants (37.5%). The most frequently identified aerobic bacteria were Escherichia coli (32; 11.6%), Enterococcus faecalis (17; 6.2%), Streptococcus agalactiae (11; 4.0%), and viridans group streptococci (9; 3.3%). However, the detection rates of Lactobacillus spp. and aerobic bacteria did not differ significantly across diagnostic groups (p=0.634 and p=0.221, respectively). Conclusions Among women with cervical precancerous lesions and cervical cancer, an increase in vaginal pH was significantly positively associated with cocci count, white blood cell count, and AV score. The higher AV scores observed in the cervical cancer group suggest that aerobic vaginitis may be associated with the progression of cervical precancerous lesions. Although the prevalence of Lactobacillus spp. and aerobic microorganisms did not differ significantly across diagnostic groups, the CC group showed a trend toward increased prevalence of aerobic microorganisms and decreased prevalence of Lactobacillus spp.