Rain gardens are increasingly recognized as effective Nature-Based Solutions (NBS) for enhancing ecological resilience in urban environments. This study investigates the ecological impact of rain gardens in Lublin, Poland, through a GIS-based assessment of vegetation dynamics between 2020 and 2025. Using Sentinel-2 imagery, Normalized Difference Vegetation Index (NDVI) maps were generated and analyzed within 300 m buffer zones around four rain garden sites. Zonal statistics revealed heterogeneous outcomes: three sites exhibited positive NDVI changes, with the University Campus rain garden showing the strongest improvement (+6.8%), while one site in John Paul II Park recorded a slight decline (-2.3%). These results highlight both the potential and variability of rain garden performance in dense urban settings. The integration of drought-resistant plant species contributed to vegetation stability, supporting microclimate regulation, biodiversity habitat, and stormwater management. Spatial analysis confirmed that rain gardens influence not only their immediate plots but also surrounding vegetation, demonstrating measurable ecological spillover effects. Overall, the findings provide empirical evidence that rain gardens contribute to localized greening and resilience within Lublin’s urban fabric. This research underscores the importance of GIS-based monitoring for evaluating NBS effectiveness and offers insights for scaling rain gardens as sustainable interventions in European cities.