With the beginning of the Parthian rule , a new style of Iranian architecture gradually emerged that, despite being influenced by Greek , Central Asian, and Iranian’s local traditions, had an independent and unique identity. One of the features of this style is the use of dome coatings on a quadrilateral field using a construction filling technique that later became a fundamental element in the Sassanidan and then Islamic architecture. Although this method has been invented by architects of the Parthian era , so far, the dome and the domed buildings in this period's architecture have not been thoroughly addressed , and little evidence has been obtained. Therefore, the necessity of studying the existing architectural evidence from the Parthian period and other sources to the better understanding of the dome element and its evolution in Iranian architecture is undeniable. The current paper is a descriptive and analytical study. Using field surveys and library research , it explores the well-known buildings, artworks, and literary pieces associated with this period to obtain and review evidence regarding the domes, domed building, their evolutionary path , and stylistic changes in different architectural elements during the Parthian’s rule) . Despite all the ambiguities , the existing pieces of evidence seem to be clear enough to guide our understanding about this architectural element and the reasons behind its usage in the Parthian architecture as well as demonstrating the relatively significant role that dome construction had in the Parthian period and shaping the architecture of subsequent periods.