The introduction of Western architectural patterns into Qajar-era Iran was a multifaceted phenomenon in which Russia, due to its geographical proximity and extensive relations with Iran, became one of the principal channels through which these patterns were transmitted. Despite the considerable body of scholarship on the political and macro-level dimensions of Iran–Russia relations, the role of socio-cultural interactions in the transmission and reception of Russian architectural patterns has rarely been examined as an independent field of inquiry. Accordingly, this study aims to elucidate the socio-cultural mechanisms through which Russian architecture was transmitted to Qajar-era Iran and to identify the main channels involved in this process. Adopting a qualitative approach and a historical-analytical method, the research is based on the content analysis of documentary and library sources, particularly the travelogues of Qajar statesmen. Rogers’ Diffusion of Innovations model is employed as an analytical framework in order to examine Russian architecture as a cultural innovation within the social context of Qajar-era Iran. The findings indicate that the transmission of these patterns occurred primarily through three intertwined channels. The first was the “architecture of coexistence and everyday life,” which operated through the presence of migrants and the formation of new residential patterns. The second was the “architecture of cultural and social institutions,” which introduced new spaces and functions such as modern schools and theaters. The third was the “intangible transmission of knowledge,” realized through language, technical vocabulary, and the skills of master builders. By transforming taste, familiarizing society with new modes of living, and providing the necessary mental and technical infrastructure, these channels laid the groundwork for the acceptance and reproduction of certain Russian architectural patterns in Iran. From this perspective, the transmission of architecture in the Qajar period was not merely the outcome of political decisions, but was also shaped through everyday interactions and social agency.