The diagrid structural system has emerged as a preferred solution for high-rise buildings because of its high lateral stiffness, reduced material usage, and aesthetic flexibility. This study compares the seismic performance of a thirty-storey steel building using two lateral load-resisting systems—(i) a conventional moment-resisting frame and (ii) a perimeter diagrid frame—both modelled in ETABS following IS 875 and IS 1893 (Part 1): 2016. The models’ dimensions are the same (30 m × 30 m plan, 3.2 m storey height). Comparative parameters include fundamental period, storey displacement, inter-storey drift, and base shear. Results indicate that diagrid systems exhibit superior lateral stiffness and drift control: fundamental period reduced by ≈ 41 %, top-storey deflection by > 50 %, and inter-storey drift by > 60 %. The 4-module diagrid had the best stiffness and deformation control of all the configurations that were examined. The findings show that the diagrid system can be used in seismically active regions and has the potential to be an affordable alternative to conventional frames.