Urban heat island (UHI) effects, intensified by urbanization and environmental changes, are critical challenges to urban thermal comfort and sustainability. This study investigates the combined role of water bodies and vegetation in mitigating microclimatic heat island effects within a campus area, focusing on their cooling impacts and interactions. Using field measurements and numerical simulations, the research evaluates the cooling effects and wind flow modifications induced by greenery and water bodies in the surrounding environment. The findings demonstrate that both vegetation and water bodies provide a significant cooling effect, reducing temperatures by 0–6 K in downstream regions, with the impact being more pronounced closer to the blue–green spaces. Furthermore, the combined application of water bodies and vegetation offers enhanced cooling effects; however, their influence on the thermal environment exhibits a nonlinear relationship. These results underscore the importance of strategic blue–green infrastructure planning in mitigating UHI effects and optimizing urban thermal environments.