Heat anomalies in metropolitan areas induced by global warming and urban heat islands (UHIs) constantly expose vulnerable citizens to health challenges, such as heat stroke. Moreover, unjust metropolitan policies have led to unequal adaptive capacities to cope with such challenges. Therefore, a comprehensive assessment of heat-health vulnerability (HHVA) in these areas is required to address the current deficiencies. The Tehran metropolitan area, as the capital city of Iran, is a case where citizens are unevenly exposed to urban heat and, in some parts, have inadequate access to essential facilities due to rapid population growth. Thus, we spatially analyse the heat-health vulnerability of the Tehran metropolitan area as a first step. We implement thermal remote sensing techniques on the Landsat 8 satellite data using a PyQGIS plugin to assess citizens’ heat exposure. Additionally, we incorporate related socio-economic, environmental, and urban planning variables to analyse sensitivity and adaptive capacity. Afterward, we recommend urban cooling solutions to mitigate the studied vulnerability. The results indicate that Districts #03 and #01 are the least vulnerable as they are less exposed to heat, and also, their under-5-year-old population rate and poverty index are low. Moreover, the considerable area of urban greenery and proper access to cooling infrastructure have improved the adaptive capacity. In contrast, Districts #09 and #21 are considered the most vulnerable areas of the case due to higher heat exposure, high poverty index, and less access to critical infrastructure. The study provides a practical framework for ongoing heat-health vulnerability assessments to address the evolving challenges of urban heat and proposes urban planning strategies enhancing heat justice and resilience across the Tehran metropolitan area. The most crucial proposed solutions are to maintain and develop blue–green infrastructure by using climate-compatible species and reduce the intensity of urban heat stress by providing sufficient shading and open spaces. A just distribution of urban cooling centres is also highly recommended.