We present a thermodynamic study of the Ta–V system based on the Calphad–Thermocalc approach. This work is part of a broader project concerning the thermodynamic description of Ta-containing low activation steels, which were developed in the past decade for applications in fusion technology. In the binary system Ta–V, the Gibbs energy functions of the liquid, the bcc solid solution and the Laves phases were determined. Conflicting information exists in the literature concerning the possible polymorphism of the Laves phase at high temperature; a preliminary assessment of the phase diagram was made without taking into account this phenomenon. Then, the C14–C15 transition was introduced for the Laves phase. The calculated phase equilibria were compared with experimental data.