Qajar architecture is a turning point in ideals and values as well as the field of diversity and contrasts in Iranian architecture and urban planning methods and tendencies. This turning point, concurrent with the gradual fade of basics of previous social identity such as ethnicity, religion, language, etc. and its movement towards concepts such as the superordinate (elites) and subordinates (people) became an outstanding instance in residential architecture in such a way that it changed the traditional homogenous and monolith structure of neighborhoods with the challenges between tradition and modernity and the use of the instrument of class differences and distinctions. The present study, conducted via a descriptive-analytical method on some case traditional and western mansions of the Qajar era, is to extract and explain characteristics of tradition and modernity in residential architecture of that era. Findings of the study show that the Qajar residential architecture passed a very tremendous and fast transformation in its passage from the traditional to the western world and regardless of no transformation in the building technology, by establishment of extroversion instead of introversion, formal and spatial changes in the circulation system, and direct modeling of elements and decorations of western architecture. However, no significant dynamics in line with utilization and completion of genuine and historical achievements of Iranian traditional architecture caused that that transformation became the field of contradictions and contrasts in Iranian residential architecture.