When coupled with ferromagnetic layers (FM), topological insulators (TI) are expected to boost the charge‐to‐spin conversion efficiency across the FM/TI interface. In this context, a thorough control and optimization of the FM/TI interface quality are requested. Here, the evolution of the chemical, structural, and magnetic properties of the Fe/Sb2Te3 heterostructure is presented as a function of a rapid mild thermal annealing conducted on the Sb2Te3‐TI (up to 200 °C). While the bilayer is not subjected to any thermal treatment upon Fe deposition, the annealing of Sb2Te3 markedly improves its crystalline quality, leading to an increase in the fraction of ferromagnetic Fe atoms at the buried Fe/Sb2Te3 interface and a slight lowering of the magnetic coercivity of the Fe layer. The method is an efficient tool to clean up the Fe/Sb2Te3 interface, which may be extended to different FM/TI heterostructures. Simultaneously to the …