Fe^III-containing aluminosilicate zeolites are present in cement-relevant and natural environments. Although Fe^III is known to occur in framework tetrahedral sites where it substitutes isomorphically Al^IIIO₄ or in extra-framework octahedral sites as free Fe(H₂O)₆³⁺, the structural incorporation process of Fe^III into different sites is little known. We aim to discern feasible pathways of Fe^III incorporation using hydrothermal synthesis methods and synchrotron-based spectroscopic analyses. Results showed that introducing either Fe³⁺ or Fe₂O₃·xH₂O initially during zeolite nucleation did not lead to Fe^III incorporation into the zeolites but only Fe₂O₃·xH₂O prevailed in both cases. However, Fe(NO₃)₃, FeCl₃, and Fe₂O₃·xH₂O affected the kind of zeolite formed. A feasible pathway to incorporate tetrahedral Fe^III in the zeolite framework was to introduce firstly Fe^III in the cage of faujasite-Y followed by a phase transformation to chabazite. This study facilitates understanding of Fe^III uptake in zeolites and of Fe^III functional sites that can contribute to immobilization of contaminants.