Conformance with the principles of passive defense in architectural works and urban planning plays a decisive role in creating stability and protecting the life and financial interests of citizens. The research method is descriptive-analytical and field and library methods were implemented to investigate the statistical population. In this research, 564 buildings in the historical city of Masouleh, being constructed based on passive defense concepts, have been investigated. The research question is as follows; How is passive defense observed in the architecture and urban planning of the historical city of Masouleh? And how can it be used for the architecture and urban planning of Iranian cities by rereading the concepts of passive defense in Masouleh? The research results indicate that the location of the city, dispersion of the buildings (vital to medium), city camouflage, confusion in the eyes of the enemy, structural fortifications of the buildings, quick repairability of the buildings, protection of urban facilities, design criteria of urban furniture, materials used in the structure and facade, form of buildings, number of entrances and exits and the presence of multi-functional spaces on the floors, small and protected openings in the facade, safe space, shelter, protective walls, compliance with building height and scale based on the importance factor, privacy, access to vital and medical places, service centers, parking lots and infrastructure facilities of Masouleh have been in line with the concepts of passive defense.