Qajarid residential-governmental settlements found in Baluchistan have a unique architecture due to the security concerns that resulted from adjacency with the borders of the neighboring countries, in addition to the special climatic and environmental conditions of the region. The concepts behind the architecture of the Qajar era had certain shared grounds that were rooted in the sociopolitical issues of that historical period and can still be observed in many Qajarid castles. This study analyzes these concepts in the architectural features of Seb Castle in Saravan County, with the aim of reviewing the architecture of the castle and identifying its spaces. The architecture of Seb Castle, which was a residential-governmental site, reflects the cultural, climatic, and geographical conditions of the region, as well as the builders’ knowledge of the local materials. In this research, which is partly historical-interpretive and partly descriptive-analytical, the prominent architectural features and ornaments of Qajarid castles in Saravan County, especially Seb, are discussed with the aim of examining the major factors that have affected the structure of these fortified buildings. The results show that the sociopolitical conditions of that era had a great impact on the structure of Qajarid castles. In addition, the study of the prominent features of Seb Castle shows that it has a special mastaba structure and that it has been constructed with the clay-alyssum mixture, a local material once commonly used in the region. Unlike other Iranian historic buildings in which common ornaments included decorative plasterwork, tile-work, mosaic, and mirrors, the interior and exterior of Seb Castle have been decorated using clay and mud.