Future sea-level rise poses substantial risks to the densely populated and economically critical coastlines of East Asia, yet coastal projections from global climate models (GCMs) remain uncertain because shallow-shelf ocean dynamics governing sterodynamic sea level (SDSL) are poorly resolved. Here we combine dynamically downscaled SDSL with other sea-level components to produce improved projections under SSP2-4.5. By 2100, regional-mean relative sea level across East Asia shelf regions rises by 61 (40–89) cm, with SDSL as the largest component (39%) and up to 18% higher than GCM-based estimates. Incorporating improved SDSL and local subsidence, we assess sea-level projections and socioeconomic risks for representative metropolitan centers. The 100-year extreme sea level rises by 23–69% by 2100, driving increases in inundated land area, exposed population and physical capital up to 58%, 238%, and 148%, respectively. These results highlight urgent coastal risks and provide a credible basis for adaptation planning across East Asia.