The old city of Jaipur is one of the most valued tourist attractions for its culture and heritage and is known for its street shopping with a backdrop of historic structures. A high influx of tourists and commercial activities resulted in the need for additional spaces, accommodated through irreversible transformations in the old cityscape. Tourists and local vendors spend most of their time on the streets, and it is essential to improve outdoor thermal comfort thereby enhancing the overall tourist experience and boosting economic activities. Hence, this research aims to investigate the relationship between the urban-built environment and outdoor thermal comfort (OTC) in the old city of Jaipur. Badi Chaupar (a junction) and Hawa Mahal Road (Commercial Street) in the old city were chosen for the study. Air temperature, relative humidity, wind speed, and surface temperatures were measured at four locations in the chosen streets in February 2023. The locations were further modelled in Envi-met (a 3D urban climate modelling tool), and the simulated measurements were validated with the onsite data. Seven different iterations were then modelled in Envi-met by including vegetation, façade projections, and water body in the base case and were simulated for the critical summer month (May) to analyze the impact of built morphology on the outdoor thermal comfort of pedestrians. The study revealed that the increase in the building heights resulted in a drastic reduction in heat stress by reducing the MRT values by 5 °C at the junction. The modifications in the setbacks and projections on the exterior facade at Hawa Mahal (Commercial Street) reduced the MRT value by 10 °C. The findings of the study can aid urban planners and designers in developing climate-sensitive urban design retrofitting strategies in traditional cities while keeping in mind the cultural and historical value of the place.