This study offers a probabilistic framework for the seismic life-cycle cost (SLCC) assessment of aging highway bridge structures in complex seismogenic zones, followed by a case-study application on a popular bridge class in Seattle (United States). The proposed framework efficiently handles the implications of differing seismic hazard scenarios (crustal and subduction earthquakes) along with time-dependent bridge deterioration mechanisms on seismic fragility and lifetime economic losses. These losses, stemming from the seismic damage-induced repair of critical bridge components, may be uncertain depending on the repair technique, availability of resources, or decision of the stakeholder. Unlike previous works that have evaluated seismic losses under a single hazard source and deterministic repair costs, this study aimed for a better approximation of the accumulated lifetime losses for aging highway