Coastal vegetation forms the ecological foundation of bioshields, providing both structural stability and biological resilience to dynamic coastal environments. This chapter examines the ecological characteristics, functional roles, and spatial organization of key vegetated coastal ecosystems—mangroves, salt marshes, seagrass meadows, and coastal dunes. It explores how species composition, zonation patterns, root and canopy structures, and physiological adaptations enable these systems to thrive under fluctuating salinity, tidal regimes, and sediment conditions. The discussion integrates ecological processes, including nutrient cycling, primary productivity, and sediment accretion, which collectively underpin the capacity of coastal vegetation to attenuate wave energy and stabilize shorelines. Emphasis is placed on ecological interactions within and between these habitats, including connectivity among mangrove–seagrass–coral reef complexes that enhance biodiversity and ecosystem functioning. The chapter also addresses threats to ecological integrity, including pollution, land-use changes, invasive species, and climate-induced stressors, which compromise both ecosystem health and protective functions. Drawing from case studies in tropical and subtropical Asia, it highlights the critical role of ecological understanding in the design, restoration, and management of effective bioshields. By linking ecological theory with applied coastal management, this chapter provides the scientific foundation for subsequent discussions on biophysical mechanisms, climate resilience, and bioshield design, reinforcing the central premise that ecological integrity is the cornerstone of sustainable coastal protection.