This study presents an integrated CFD–FEA thermal analysis of an aft-fan module designed for a mini turbojet engine, employing a hierarchical approach that combines one-dimensional heat-transfer formulations, two-dimensional disc conduction–convection models, and three-dimensional CFD-assisted solid thermal simulations. CFD-derived convection coefficients and secondary air system (SAS) cooling conditions were mapped onto the solid domain to obtain a realistic temperature field under combined hot- and cold-flow conditions. The results indicate a maximum metal temperature of ≈979 K on the turbine rotor blades, while the fan-side components remain near ≈294 K, establishing a pronounced through-disc thermal gradient driven by the 1045 K turbine inlet gas. The analytical and three-dimensional numerical models produced closely matching temperature distributions along the rotor and casing, demonstrating consistency between the modelling approaches. Materials were selected based on the predicted thermal loads: Inconel 738 for the hot-side components, Ti–6Al–4V for the cold-side aerodynamic surfaces, Inconel 718 for the highly loaded covers, and AISI 410 for the shaft. The presented workflow provides a systematic numerical framework for the thermal assessment of aft-fan modules and offers new insights into heat-load management and temperature-driven design constraints in next-generation mini and micro turbojet propulsion systems.