Wood-steel hybrid (WSH) elements have become a trend in the construction industry due to their lower environmental impacts and high load capacity. However, the challenge of fire resistance remains crucial for the wood industry's advancement as a construction material. The proposed WSH slab, consisting of two laminated veneer lumber (LVL) beech panels combined with a corrugated steel sheet, offers enhanced thermal insulation due to the inner cavity within the system. This research aims to numerically simulate the fire performance of the proposed WSH slab element using a transient heat transfer model. The objective is to evaluate the time-temperature behavior of each individual component within the system, assess the charring rate of LVL panels, and validate the numerical results through experimental fire tests. The simulation results of the time-temperature profiles highlight the significance of the internal cavity's size and shape in influencing the system's heat flow. The analysis of different thicknesses and heights of the corrugated steel sheet shows a substantial impact on the charring initiation time of the upper LVL layer. The numerical temperature profiles of the components exhibited the same behavior as the experimental profiles. Additionally, the numerical charring rate of the upper LVL showed an average value of 1.09 mm/min, while the experiments showed an average value of 1.03 mm/min. However, the numerical temperature profiles showed deviations up to 11% in some points from experimental results, which can be attributed to factors such as varying moisture content in LVL layers, shifts in thermocouple positions, wood water evaporation rates, and unpredictable crack formation. Future research is recommended to prioritize a more in-depth investigation of critical parameters for thermal studies, including material density, thermal conductivity, and thermal mass capacity with temperature dependency.