Seismic performance of reinforced concrete (RC) frame buildings has long been a subject of paramount importance in structural engineering, particularly in earthquake-prone regions. Among the various structural systems employed to enhance seismic resilience, diagrid systems have garnered considerable attention due to their inherent stiffness, efficiency in load distribution, and aesthetic appeal. Diagrid system also enables the construction of tall, irregular and intricate architectural designs with enhanced efficiency and structural integrity. However, the impact of different diagonal angles within diagrid systems on the earthquake-resistance response of RC frame buildings remains a pertinent research area. Through comprehensive numerical simulations and analyses, this research investigates the RC frame buildings with diagrids featuring diverse diagonal angles for their seismic resistance capability. The current research also focuses to determine the best angle for the diagonal member’s best shape, as well as a comparison with conventional buildings devoid of diagrid system. 30-storey buildings with square and rectangular plan areas are examined while keeping the floor area and column area consistent and arranging the diagonal members accordingly. The diagrid systems of 1-storey, 2-storey, 3-storey, 4-storey, 5-storey, and 6-storey featuring different inclination angles are analyzed in terms of their ability to mitigate seismic forces, reduce structural deformations, and enhance overall building performance during seismic events. All models are assumed to be situated in seismic zone V of India and in medium type soil. Seismic performance is evaluated via response spectrum and nonlinear time history analyses. The findings of this study provide valuable insights into the seismic response of RC frame buildings equipped with diagrid systems, offering guidance for structural engineers and designers aiming to optimize structural performance and resilience against seismic hazards.