A critical assessment of the Fe-Sb system was carried out by using a computerized technique. Both the liquid and solid solution phases were described by regular solution models. Nonstoichiometric phase, ε-FeSb, was modeled as (Fe)(Fe,Sb), and FeSb2 was treated as a stoichiometric compound. A set of parameters describing the Gibbs energies of the different phases was optimized by using the existing phase diagram information and thermodynamic properties under one atmosphere. Assessed phase diagram and thermodynamic data are presented and compared with experimental data.