This cross-sectional survey study was carried out on the Sundarbans mangrove forest resource- dependent communities (SMFRDCs) of three southwestern coastal districts of Bangladesh, namely Satkhira, Khulna and Bagerhat. Administering a semi-structured interview schedule (SSIS), data were collected from 782 SMFRDCs following a multistage stratified random sampling approach, and data were analyzed using IBM SPSS Statistics v25 for Windows. Findings indicate that the prevalence of social, economic, physical, institutional, attitudinal, and environmental vulnerabilities were 72.5% (95% CI: 69.2%-75.6%), 67.3% (95% CI: 63.9%-70.5%), 68.8% (95% CI: 65.4%-72.0%), 70.1% (95% CI: 66.7%-73.3%), 85.2% (95% CI: 82.5%-87.6%), and 82.6% (95% CI: 79.8%-85.2%), respectively; while the prevalence of overall household vulnerability was 66.2% (95% CI: CI: 62.8%-69.6%). Among the factors associated with the overall household vulnerabilities were age ( chi ^ 2 = 48.962 , p < 0.001 ) education ( chi ^ 2 = 14.245 , p = 0.007 ), occupation ( chi ^ 2 = 20.94 , p = 0.002 ) experience ( chi ^ 2 = 18.383 p = 0.001 ) , and district ( y ^ 2 = 14.441 , p = 0.006 ) From the findings it is apparent that the SMFRDCs in the selected study areas were more vulnerable, attitudinally, and environmentally, and different socio- demographic factors were the key determinants of their vulnerabilities. It is, therefore, strongly recommended that government and non-government organizations, together with their international development partners should devise comprehensive and holistic plan to reduce the vulnerabilities of the SMFRDCs by addressing individual and community levels factors in order to ensure sustainable livelihoods for these marginalized people.