Experimental diffusion data in Ni-rich fcc Ni-Nb-Ti alloys at 1273 K was measured by electronic-probe microanalysis and the interdiffusion coefficients have been determined using Whittle and Green method. The atomic mobilities of Ni, Nb and Ti in Ni-Nb-Ti alloys have been obtained through assessing the interdiffusion data critically with the DICTRA software. Comprehensive comparisons between calculated and experimental diffusion coefficients showed that the atomic mobilities obtained in this work could well reproduce the experimental data. And the validity of the diffusion mobilities was tested by simulating the concentration-distance profiles and diffusion paths in diffusion couples.