A thermodynamic description of the Ti-Al-Fe system was established with reassessed Ti-Al and Ti-Fe binary systems using density function theory (DFT) data. All stable and metastable end members of BCC_B2, BCC_D03/B32, BCC_L21, inverse BCC_L21, Laves C14, D019-Ti3Al, L10-TiAl, Ti Al2, Ti3Al5, D022-TiAl3, τ2 and τ3 in the Ti-Al, Ti-Fe and Ti-Al-Fe systems were energetically defined with available experimental data and DFT calculations, reaching reasonable consistency. The ternary description was used to successfully calculate the A2-B2-L21 transformation in Fe-rich corner and A2-B2 transformation in Ti-rich corner, allowing the design of Ti-rich and Fe-rich alloys in this system.