Ecosystem service assessments are crucial for sustainable water area management. Previous studies and actions on waterfront area management often emphasized merely the saving and use of water resources per se, ignoring the safeguarding of hydrological source ecosystems and assurance of sustainable provision capacity of water supplies. Using the Yangtze River Delta Ecological Green Integration Demonstration Zone (demonstration zone) as an example, this study integrated ecosystem service assessment into waterfront area management in an urbanizing region. We evaluated and mapped four ecosystem services—carbon sequestration, water purification, stormwater regulation and climate regulation—in the demonstration zone in 2020. We examined ecosystem service quantities, spatial distributions and economic values to inform policy balancing development and the environment. Our results show that ecosystem services provide significant benefits to waterfront areas: the zone furnished substantial ecosystem services, sequestering 544,900 tons of atmospheric carbon dioxide (USD 2.03 million), eliminating the total material quantities of nitrogen and phosphorus pollution of 47,700 tons and 13,900 tons (USD 66.31 billion and USD 20.17 billion, respectively), and retaining over 467.48 million cubic meters of stormwater runoff (USD 1756.35 million) and total material quantity of climate regulation amounts to 65.13 billion kilowatt hours (USD 5.10 billion). However, these service provisions varied spatially. Wujiang District provided the most ecosystem services overall, while Qingpu District had the highest per-unit intensities in stormwater regulation. Policy, planning and action should consider ecosystems providing security and prosperity. Managing the trade-offs between development and environment, reducing risks and cultivating resilience necessitates safeguarding ecosystem service potential.