An important aspect to take into account in the process of prevention, mitigation, preparedness and response to the catastrophes is the risk assessment in transboundary areas that needs a harmonized cross-border approach. Indeed, transboundary risk assessment cannot be based directly on national risk assessment because the neighbouring countries use different risk assessment methodologies and levels of detail. To address this issue, a harmonisation process should be implemented with the aim to establish the use of shared approaches and employ common data types and analysis models, which allow representing the impact of the seismic hazards in a shared framework among the countries. This paper illustrates the proposed methodology for seismic risk assessment in the area on the border between Italy and Slovenia, in particular in the region near Gorizia and Nova Gorica. This activity is one of the products of the BORIS project (Cross BOrder RISk assessment for increased prevention and preparedness in Europe) that focuses on the assessment of seismic risk and flood risk, having cross-border impact potential in several countries participating in the Union Civil Protection Mechanism. Furthermore, a web-based platform developed to facilitate the storage and visualization of data, models, and the representation of damage and impact data following a common metrics approach is presented.