Phase relations of Cu-Ni-Ti ternary system have been experimentally investigated and thermodynamically assessed. Firstly, part of phase relations in the Cu-Ni-Ti ternary system at 800 degrees C was established by analyzing Ti/Cu-Ni diffusion couple and alloy samples with EPMA (Electronic Probe Micro-Analysis). The Cu4Ti3+CuTi+NiTi equilibrium reported in literature was presently modified to a three-phase equilibrium CuTi+NiTi+tau(1) in the 730-830 degrees C temperature range. Based on the measured phase equilibria and those experimental investigations about Cu-Ni-Ti system and in combination to the three binary boundary systems optimized in literatures, thermodynamic parameters of various phases in this system were reasonably modeled through CALPHAD (CALculation of PHAse Diagram) approach. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.