Bangladesh’s rapid urbanization, particularly in medium-sized cities like Rajshahi, has led to significant environmental challenges. This study uses a GIS-based Multi-Criteria Decision Analysis (MCDA) methodology to quantify how Green Infrastructure (GI) affects urban sustainability inside Rajshahi City Corporation (RCC). The geographical distribution of GI was evaluated using 2024 Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI), satellite images, and population density data. About 22% of RCC’s metropolitan area, mostly in regions with high LST (31–40 °C) and low NDVI (<0.3), is under the Very High Priority zone for GI treatments, according to the data. Green space limitations are especially noticeable in high-density regions with LSTs above 35 °C, such Wards 3 and 6. On the other hand, parklands and densely vegetated regions (NDVI > 0.6) near the Padma River saw lower surface temperatures (20–25 °C). Key areas where green infrastructure might reduce the impacts of UHI, improve air quality, and make areas more liveable were identified by the MCDA model. The study emphasizes the need for integrated climate adaptation policies and GIS tools in planning sustainable cities in developing countries, highlighting the importance of urban greening strategies and scalable solutions for environmental pressures due to rapid urban growth. This study determined which Rajshahi priority areas needed Green Infrastructure interventions, especially those with high surface temperatures and little vegetation cover. The results highlight how GI contributes to the improvement of ecosystem services like air quality and urban cooling.