<p>Health and wellness modernization is increasingly viewed as part of urban sustainable development, yet evidence on how health and wellness modernization varies within urban agglomeration remains limited. This study develops a city-level index of urban health and wellness modernization (HWML) for 41 cities in the Yangtze River Delta Urban Agglomeration, China, from 2014 to 2023, covering medical resources, health security, ecological environment, social development, and education and technology. Using entropy-weighted TOPSIS, we measure HWML and examine temporal change. We characterize spatial dynamics with the standard deviation ellipse, decompose inequality with the Dagum Gini coefficient, assess subsystem coordination using the coupling coordination degree and equilibrium entropy models, and identify key bottlenecks via obstacle factor diagnosis. HWML increases overall but remains spatially stratified, with a persistent south and east advantage. Inter-regional differences account for most inequality. Health security, education and technology, and medical resources emerge as the main constraints on more balanced progress. The results provide policy-relevant evidence for coordinated resource allocation and collaborative governance to support more balanced health and wellness modernization in integrated city-regions.</p>