Abstract: Objective Breast cancer poses a major health threat to Chinese women, and the suboptimal early diagnosis rate is closely associated with insufficient public awareness and inadequate health education. This study, for the first time in China, conducted a multi-setting survey on breast self-examination (BSE) among women aged 40 years and above based on the Health Belief Model (HBM), with a specific focus on analyzing the HBM-related factors influencing BSE practice in this population. Methods From June 2024 to June 2025, a total of 3,954 women aged 40 years and above were enrolled from three settings in Beijing:a large community, the breast surgery outpatient clinic of Peking Union Medical College Hospital (random hospital group), and a physical examination center. Face-to-face interviews were conducted to collect data on demographic characteristics, health behaviors, and core HBM constructs (perceived benefits, perceived barriers, cues to action, and self-efficacy-related indicators). Multivariate logistic regression was used to identify factors associated with BSE practice in each setting. Results Significant differences were observed across the three groups in age, education level, occupation type, family history, and regularity of physical examination (all P<0.001). The proportion of irregular physical examinations was highest in the random hospital group (45.7%), followed by the community group (10.9%) and the physical examination center group (5.5%); the reasons varied, with "unnecessary" being predominant in the hospital and examination-center groups (91.9% and 72.0%, respectively), whereas "inconvenient access (lack of accompaniment)" (34.1%) and "economic constraints" (24.6%) were the main barriers in the community group. Although the awareness rate of BSE benefits was relatively high in all groups (up to 94.6% in the community group), the rates of knowing correct BSE methods (19.1%-35.4%) and regular BSE practice (7.8%-27.3%) were markedly low. Multivariate regression revealed setting-specific influencing factors:in the community group, women aged ≥ 65 years (OR=0.993, 95% CI:0.988-0.997) and those unaware of BSE methods (OR=0.372, 95% CI:0.370-0.374) had significantly lower BSE practice rates; in the random hospital group, those unaware of BSE methods (OR=0.813, 95% CI:0.775-0.852) had lower BSE practice rates; and in the physical examination center group, those unaware of BSE benefits (OR=0.509, 95% CI:0.474-0.546) had lower BSE practice rates. Conclusions The completion rate of BSE remains low across all populations, which is associated with women's lack of mastery of correct BSE methods and insufficient health beliefs. Future breast cancer prevention and control education efforts should be more in-depth and extensive, with targeted strategies based on the characteristics of populations in different settings to improve women's BSE practice rates and promote early detection and intervention of breast cancer.