The Fe-Sn-Zr system has been studied by first principles calculation and modelled with the Calphad method using the literature and new experimental data. The work includes a revision of Fe-Sn and Fe-Zr systems. Our experimental study has confirmed that the W5Si3 phase (stoichiometry Zr5Sn2,3Fe0,7) is stable at 1350 °C but also down to 1000 °C. Moreover, the crystal structure of the X" phase has been determined. The formation enthalpies of all the ordered configurations of the C15, C16, C36, E1a phases and the stoichiometric Fe5Sn3, Fe3Sn2, FeSn, FeSn2, Fe23Zr6, FeSn2Zr6 (θ), Fe36.36Sn36.36Zr27.27 (N) et Fe14.39Sn43.47Zr39.13 (X'') compounds have been calculated using the Density Functional Theory (DFT). The mixing enthalpies of the A1, A2 and A3 binary solid solutions have been calculated using the Special Quasirandom Structures (SQS) and DFT calculation. From these new experimental and calculated data, new thermodynaùic assessments are proposed for Fe-Sn, Fe-Zr and Fe-Sn-Zr systems. 2