ABSTRACT Carbon atom recombination and etching of the surface of nanodiamond (ND) by hydrogen plasma and their effects on the dispersion and the tribological properties of a polytetrafluoroethylene (PTFE) nanocomposite coating were investigated. The surface-modified ND samples subjected to plasma treatment were characterized using FESEM, HRTEM, Raman spectroscopy, FT-IR spectroscopy and XPS. The results showed that the plasma treatment facilitates etching and recombination of the ND surface and modifies the crystallinity of the graphitic amorphous carbon. The tribological properties of the PTFE-based nanocomposite coatings prepared with the modified ND depended on the content of sp 3 -bonded carbon on the surface and the crystallinity of the ND. Hydrogen plasma treatment caused a significant improvement in the dispersion and tribological properties of the PTFE/ND nanocomposite coating due to surface modification of the ND.