This study presents a detailed seismic analysis of a cable-stayed bridge subjected to moving vehicular loads using both IRC (Indian Roads Congress) and AASHTO (American Association of State Highway and Transportation Officials) loading standards. The structural behavior of the bridge was evaluated using SAP2000 software, with a specific focus on the influence of different pylon shapes on the dynamic performance of the structure under combined imposed and seismic loading conditions. The analysis reveals that the diamond-shaped pylon offers superior performance compared to other geometries. It exhibits up to 17% lower natural time period, leading to reduced natural frequency and thereby minimizing fatigue-related displacement. The base shear is also observed to be 22% lower than that of the single-shaped pylon, contributing to better energy dissipation during seismic events. In terms of displacement, the diamond pylon demonstrates a 22% reduction, confirming its stability under both lateral and vertical loads. Comparing the two loading standards, displacement values under AASHTO loading are approximately 7% lower than those under IRC, highlighting the impact of load definitions on bridge response. Additionally, axial forces and bending moments in the pylons are significantly reduced with the diamond shape—16% and 19% lower respectively under IRC, and 12% and 16% lower under AASHTO—further indicating the structural advantages of this geometry. The distribution of tensile forces in the stay cables also aligns with expectations, with higher forces in outer cables and 10% to 7% lower forces under IRC and AASHTO, respectively, for the diamond-shaped pylon compared to the single shape. The study concludes that the diamond-shaped pylon configuration enhances structural performance and resilience, making it a favorable choice for seismic-prone and high-traffic regions when evaluated under both IRC and AASHTO standards. Keywords: Cable-stayed bridge, Seismic analysis, Pylon shapes, Moving loads, IRC and AASHTO standards, SAP2000