The phase equilibrium and thermodynamic information of the Nb-W-C system was reviewed and assessed by using thermodynamic models for the Gibbs energy of individual phases. The assessment was based on the recent evaluations of the W-C, Nb-W and Nb-C, which was revised in the present work taking ternary information into account. The model parameters were evaluated by fitting the selected experimental data by means of a computer program. A consistent set of parameters was obtained, which satisfactorily describes most of the experimental information.