Abstract The Langmuir–Blodgett (LB) films of fatty acids including stearic acid (SA), arachidic acid (AA) and behenic acid (BA) and that of MoS 2 nanoparticles modified with dialkyldithiophosphate were prepared on a glass substrate. The tribological properties of the LB films were systematically investigated, and the structural changes of the LB films during friction process were analyzed with Fourier transform infrared (FTIR) microscopy and X-ray photoelectron spectroscopy (XPS). It has been found that the LB films of fatty acids and surface-modified MoS 2 nanoparticles all decrease the friction coefficient of a glass/steel frictional pair. The LB film of surface-modified MoS 2 nanoparticles registered much higher antiwear life and load-carrying capacity than the fatty acid LB films. The transfer of the LB film onto the counterface was observed and different LB films underwent different tribochemical changes during the rubbing process. The friction and wear mechanism of the LB films is also discussed.