Cable-stayed bridges are critical components of modern transportation infrastructure, but their vulnerability to seismic events presents substantial risks to their long-term performance and safety. This paper focuses on the assessment of seismic damage in the lifecycle risk cost calculation for cable-stayed bridge infrastructure. The fragility method is utilized as a key approach to quantify seismic vulnerability and estimate associated risk costs throughout the bridge’s lifespan. Seismic fragility curves are developed by analyzing the structural response to various earthquake scenarios, providing a probabilistic representation of the bridge’s performance based on ground shaking intensity. This facilitates the evaluation of potential damage levels and their corresponding costs. The risk cost calculation encompasses direct expenses, including repair and replacement of damaged components, and employs statistical methods to estimate expected expenses. Stakeholders and decision-makers can utilize this approach to make informed choices regarding risk reduction investments, maintenance planning, and long-term sustainability considerations. A specific case study is conducted on a cable-stayed bridge, focusing on longitudinal seismic waves. The findings reveal that the main tower exhibits greater resilience compared to the tower abutment. The failure probabilities of slight, moderate, severe, and absolute damage for the main tower are determined as 9.8%, 1.1%, 0.3%, and 0.2% respectively, while the corresponding failure probabilities for the main abutment are 35.2%, 21.1%, 7.4%, and 2.9%. The maintain life cycle cost associated with seismic events for this bridge is estimated at 0.548 million USD. These results provide valuable insights for decision-making processes regarding risk reduction strategies, maintenance planning, and long-term sustainability considerations.