The aim of this paper is to provide a systematic understanding, through simulation-based assessment, of how contemporary urban planning affects the bioclimatic features of existing historic architecture. An emblematic early 20th century Brazilian building, the Casa das Rosas in São Paulo, has been chosen as a case study to see how the deep transformation of its surroundings has altered its indoor conditions. Taking into account both the original and the current urban and environmental conditions, a two-step assessment is conducted by moving between two levels of simulation: the urban- and building-scales. The urban-scale simulations characterize the microclimate parameters (temperature, humidity, and wind speed) that will represent the boundary conditions for the building-scale simulation. EnergyPlus and DIVA-for-Rhino were used to assess the bioclimatic features in terms of indoor thermal and visual comfort levels respectively. Despite the revival of passive design solutions derived from historic architecture, studies of the influence of contemporary urban settlements on their comfort behavior are still quite limited. Outcomes from our simulations show that urban planning can have a significant impact on the indoor light levels of historic buildings, but that the average temperature conditions are not significantly affected. We expect that the results would show a bigger difference if anthropogenic heat sources were taken into account, especially for outdoor comfort conditions.