X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) were used to investigate the effect of tantalum addition on the TiN thin films structure. Both the HRTEM and selected area electron diffraction have showed that the films possess a fine grained polycrystalline structure with an average grain size in the order of 10 nm. The chemical composition of the films was determined by the use of the Ti2p, N1s and Ta4f core level peaks. The analysis of Ta4f core level revealed the presence of Ta-N bond indicating that tantalum atoms can occupy the titanium sublattice sites. Moreover, the XPS spectra revealed the presence of Ta2O5 in the films.