Although urbanization is associated with vegetation decline, specific urban conditions may instead stimulate vegetation growth, producing offset effects. However, the spatiotemporal evolution and underlying drivers of these effects remain insufficiently understood, hindering their integration into sustainable urban planning. Here, using satellite observations, we assessed the offset effect index (t) across 806 built-up areas in China from 1985 to 2024, quantifying both its spatial distribution and temporal evolution. Our analysis reveals that urban vegetation growth has compensated for approximately 69.7% of urbanization-induced green space loss, a phenomenon prevalent in 86% of Chinese cities, highlighting its widespread and significance. Spatially, the strongest t occurred in the humid North China Plain, whereas weaker effects were observed in arid Northwest and Inner Mongolia, highlighting a strong climatic control. A significant temporal trend emerged: t demonstrated a progressive intensification; concurrently, the urbanization intensity required to reach peak t declined, indicating increasing developmental constraints. Importance analysis revealed that elevation exerted the strongest impact on t. Dominant drivers also varied across climatic zones; population density was most influential in the north temperate zone, whereas in plateau climates only urbanization intensity contributed positively. These results highlight the adaptive potential of urban ecosystems under rapid urbanization and demonstrate that urban environments can act as catalysts for vegetation growth, while also underscoring the constraints imposed by development pressures. Thus, these findings provide scientific evidence for integrating ecological resilience into urban planning and management.