Coastal and marine tourism is expanding rapidly in Bangladesh. However, empirical evidence regarding its ecological consequences remains limited. This study evaluates tourism-induced pressures on coastal and marine biodiversity across three popular and ecologically distinct destinations: the Sundarbans mangrove area, the sandy coast of Kuakata, and the coral-bearing offshore St. Martin’s Island.  Tourism-related stressors were assessed through field observations, biodiversity surveys, and semi-structured interviews conducted between July 2022 and June 2023.  Using integrated biodiversity surveys and mixed methods, socioeconomic surveys, the results show a pronounced spatial overlap between tourism hotspots and ecologically sensitive habitats. Extensive fish, coral, invertebrate, mangrove, and seaweed diversity was documented across all study sites (The Sundarbans: 14 fishes, 11 aquatic invertebrates, 8 conservation-significant taxa; Kuakata: 21 marine fishes, 12 crustaceans, 8 molluscs, 3 threatened fishes, 13 mangrove and coastal flora, 9 birds; St. Martin’s Island: 6 coral, 18 fishes, 31 invertebrates, 24 molluscs, 20 seaweeds, 8 dominant coastal flora). Across three study sites, tourism activities overlapped spatially with ecologically sensitive habitats, viz., mangrove channels, estuarine nursery grounds, reef flats, intertidal zones, and wildlife corridors. Observed pressures included destructive fishing operation, vessel traffic, anchoring damage, coral trampling, waste accumulation, shoreline modification, and wildlife disturbance. Interview-based thematic analysis further indicated increasing resource-use conflicts and livelihood dependency interacting with tourism expansion. The findings validate that unmanaged tourism is contributing to localized habitat degradation and biodiversity stress in Bangladesh’s priority coastal sites. Site specific management interventions, including spatial zoning, visitor carrying-capacity limits, no-anchor reef protection areas, sustainable fishing, strengthened waste management systems, and community-inclusive co-management are urgently required. Integrating tourism governance with ecosystem-based management frameworks will be essential to safeguard biodiversity while sustaining coastal livelihoods and advancing national commitments to relevant Sustainable Development Goals.