Transition metal borides such as TiB2±x and WB2±x are promising materials for protective coatings, because they combine high hardness with self-lubricating properties. At high temperatures, they form a thin B2O3 layer that helps reduce friction. Super-stoichiometric TiB2.9 shows lower friction than TiB1.5 because the extra boron produces more lubricating oxide. Similarly, α-WB2±z coatings also exhibit self-lubrication properties. However, they tend to stabilize in the sub-stoichiometric form, resulting in reduced amounts of boron available for oxidation. The tribological data are further correlated with XPS, XRD, and TEM analyses, offering new insights into the lubrication mechanisms of boron oxide in thin films.