Although extensive research efforts have focused on the design and response of structures under isolated earthquake loading or tsunami inundation, very few studies have considered their combined effect. Moreover, very little research has been conducted on heavy timber structures such as timber pile bridges. This study focuses on the performance of timber pile bridge substructure retrofitted with fiber reinforced polymer (FRP) composites subjected to earthquake-tsunami hazard events. Due to their simplified design, and susceptibility to deterioration, timber pile bridges may not have the capacity to resist extreme loads. FRP composites have become a popular material for structural retrofits due to their high strength, versatility, and because they do not corrode. Experimental studies have shown FRP composites can significantly improve the strength and stiffness of timber piles. In this study, the multi-hazard analyses are performed using the Open System for Earthquake Engineering Simulations (OpenSees) framework. Recently, OpenSees was extended to solve fluid-structure interaction (FSI) problems using the particle finite element method (PFEM). This new capability is used to simulate the tsunami loading. The goal of this study was to develop a multi-hazard interaction diagram to evaluate the impact of timber deterioration, and the level of FRP retrofit on the performance of the structure. The interaction diagram provides a useful means for engineers to estimate the performance of a structure and can be used to aid in repair decision-making.