Population growth and physical expansion of metropolitan areas in recent decades have led to changes in spatial structure and accessibility patterns across different parts of cities. The population of Karaj increased from 14,526 in 1956 to 1,592,492 in 2016. Understanding spatial structure and assessing differences in accessibility across different urban areas are essential for sustainable planning and the realization of spatial justice. This study aims to evaluate the spatial structure and integration of the road network in the metropolis of Karaj and to examine differences in accessibility at different spatial scales using the Space Syntax approach. The study is applied in terms of its purpose and descriptive–analytical in terms of its nature. The road network data of Karaj were analyzed using Depthmap. Space Syntax indicators, including Connectivity, Choice, Integration, and Total Depth, were calculated at Global, R2000, R1200, R800, and R300 scales and processed in GIS. The findings show that the spatial structure of Karaj generally follows a center–periphery pattern, with the intensity of this pattern varying across analytical scales. The central areas, including the city center, Ghand-e Qand, Chahar Sad Dastgah, Jahanshahr, Azimieh, and Gohardasht, have higher levels of centrality and integration. In contrast, Hesar Bala, Qezel Hesar, Bagh-e Sib, and parts of Mehrshahr exhibit lower integration and greater spatial depth. These differences are more evident at the R300 and R800 scales. The results indicate that differences in accessibility depend not only on the extent of road network development but also on the way the network is connected and organized. Improving connectivity, creating cross-connections, and strengthening local centers, particularly in peripheral and poorly connected areas, can contribute to improving accessibility and spatial justice in the metropolis of Karaj.