Particularly in urbanized areas, the intensification of urban heat islands (UHI) presents serious environmental and health risks. The cooling effects of local and exotic tree species on Karachi’s UHI are compared in this study. Five urban sites were selected to study seven different tree species: Eucalyptus, Delonix regia, Azadirachta indica, Conocarpus erectus, Ficus virens, and Cocos nucifera. To ascertain species-specific cooling potential, microclimatic parameters such as surface temperature, ambient air temperature, and light intensity were measured between 7:00 a.m. and 4:00 p.m. The time was chosen from sunrise to the point where sun is nearly setting. The efficiency of cooling varied significantly between species, according to the results. When it came to lowering surface temperatures and light intensity, native species like Azadirachta indica and Ficus virens outperformed exotic species like Conocarpus erectus. At 12:00 p.m., Ficus virens showed the greatest temperature decrease of 23.25 °C and the most significant decline in light intensity of 93,564 lx simultaneously. Conocarpus erectus, on the other hand, demonstrated comparatively inferior cooling efficiency even if it helped mitigate UHI. The results emphasize how important native trees are to sustainable urban cooling and show how they can be an affordable way to counteract the effects of UHI as people use nonrenewable electricity in order to mitigate UHI. In order to improve thermal comfort, lessen heat stress, and increase environmental resilience overall, this study highlights the importance of including native tree species into urban development. A framework for optimizing green infrastructure in urban ecosystems is provided by the study to policymakers.