The Ti-V-O system has been assessed using the CALPHAD method based on recent assessments of its binary systems. The present work focuses on the following oxide sub-systems: V2O3-TiO2, VO2-TiO2, V2O5-TiO2 and V2O3-Ti2O3-TiO2. The liquid phase was described by the ionic liquid model while the solid solution oxide phases were modeled using a two-sublattice model within the framework of the compound energy formalism. The available experimental data were critically evaluated and a consistent set of thermodynamic model parameters was obtained. Satisfactory agreement between calculated and experimental information especially of the stability, solubility and phase relations of various oxide phases is achieved. Reliable predictions of oxygen solubility in Ti-V alloys can be made using the present thermodynamic descriptions.