The rapid increase of urban surfaces with high albedo in Ho Chi Minh City has been documented to correlate with certain urban health issues such as increased thermal discomfort and mortality rate. In such dense cities, using blue-green infrastructure for the urban surfaces can be a potential mitigation solution. Several studies have discussed this measure; however, very few have numerically and spatially examined its impacts. Therefore, this study aims to investigate the potential effects of green-blue infrastructure on outdoor thermal comfort using scenario analysis. Taking a residential block in a developed area of Thu Duc District as a case study, the authors used ENVI-met for thermodynamic simulations to calculate the Physiological Equivalent Temperature (PET) index values. Input data were gathered from the open-access sources involving geographic, geometric, and meteorological characteristics. On the hottest day of the year, the PET values (25.00-45.3°C) revealed a high level of thermal perception during the active daytime, from 07:00 to 17:00. Extreme heat stress during this time can cause health-related risks. Cooling effects were then investigated by applying blue-green infrastructure on different urban surfaces. By using green roofs, green walls, and water bodies, thermal discomfort was found to be less severe along the greenery surfaces (PET reduction by 0.7°C), on a surrounding the water surface (PET reduction by 3.0°C), and potentially reaching a larger area following the prevailing wind direction. The impact area, location, and the numerical results of the cooling effects imply that blue-green infrastructure could be a potential measure in urban design to mitigate heat islands in the hot-humid region. Additionally, such measures can provide further public health-related benefits, especially regarding psychological impacts.