An acoustic emission (AE) technique was developed to study the adhesional characteristics of TiN thin film deposited on SKD and SKH steel using plasma CVD technique. Pin-on-disk type wear testing machine with acoustic emission sensor was used to measure the relationship between the AE count rates monitored through the pin and the wear rate of the steel materials deposited by the thin film and to investigate the adhesional strength of the film. In addition, the applicability of the Root Mean Square (RMS) value derived from the AE signal to the evaluation of the wear and frictional properties of the steel was discussed, The experimental results showed that the relationship between the wear rate and the RMS value was significantly dependent upon the mechanical properties of the pin with a deposition of the film. The frictional coefficient derived from the interface between the pin and the disk increased slightly with an increase in the amount of indentational load applied to the pin. It may also mentioned that the present results demonstrate sufficient promise of the ability of the AE technique to be applied to the evaluation of the thin film deposited on metallic materials.