Timber-steel hybrid systems utilize timber as main construction material, but also take advantage of the ductility and stiffness that steel provides. For a novel hybrid system to gain recognition, experimental data must be supported by numerical analysis to predict its structural performance. “Finding the Forest Through the Trees” (FFTT) is one proposal for a timber-steel hybrid system using mass-timber panels as shear walls and floor slabs connected with steel header beams. This thesis presents research to evaluate the seismic performance of the FFTT hybrid system using experimental methods, numerical modeling, and reliability analysis. The FFTT system was investigated on two levels: i) component design, and ii) system design. On the component level, the strength, stiffness, ductility, and failure mechanisms of the two key connections were evaluated experimentally. CLT (Cross Laminated Timber) wall to steel beam connection tests results demonstrated that appropriate connection layouts can lead to the desired failure mechanism while avoiding crushing of the mass-timber panels. For the hold-down connection, a modified HSK (Holz-Stahl-Komposit) assembly with high force and stiffness capacity together with ductile behaviour was proposed. On the system level, the seismic response of the FFTT system with different ductility values was investigated using nonlinear 2D and 3D models subjected to a number of ground motion acceleration records. The seismic reliability with various uncertainties was analysed in order to investigate the FFTT system from a performance based approach. Based on the results, an appropriate seismic force reduction factor specific to the FFTT system was proposed. Finally, a feasibility study confirmed the possibility of the practical application of this system. This thesis can serve as a precursor for developing design guidelines for tall wood-hybrid building systems in seismic regions.