The underground tombs of the Elamite period in present-day Khuzestan Province are among the most significant examples of funerary architecture in Iran. One of their most distinctive architectural features is the barrel vault, constructed using various materials and building techniques. Among these monuments, the underground tombs of Susa are particularly notable for their use of trapezoidal-shaped bricks and the diversity of their construction methods. Investigating the structural characteristics of these vaults contributes to a better understanding of ancient building technologies and supports conservation approaches based on the physical authenticity of historic monuments. This study aims to identify and analyze the structural characteristics of Elamite vaulted tombs, with particular emphasis on roofing techniques, vault construction, and the use of molded trapezoidal bricks. Fifteen vaulted tombs attributed to the Elamite period, including ten examples documented by de Mecquenem and five reported by Ghirshman, were selected for analysis based on archaeological reports and field investigations. The research combines documentary studies and field surveys within a historical–interpretive framework. The main research question addresses the construction characteristics of mud-brick and brick barrel vaults built with trapezoidal-shaped bricks in the Elamite tombs of Susa.The findings indicate that the vaults were primarily constructed using a pitched-vaulting technique supported by the rear wall, while short vertical or slightly inclined walls commonly served as springing supports. In some cases, a combination of pitched and radial (Roman) vaulting methods was identified. The molded trapezoidal bricks enhanced structural stability and facilitated construction. Other important findings include the use of vault rises greater than the span in small chambers and the application of three different methods for controlling the inclination of vault courses. These results suggest that this construction technology developed at Susa before its appearance at Haft Tappeh and demonstrate a progressive refinement in the use of standardized trapezoidal bricks for the construction of formwork-free pitched barrel vaults in Elamite architecture.