The tribological performance of graphene oxide (GO), graphitic carbon nitride (g-C 3 N 4 ), and their mixed (g-C 3 N 4 /GO) aqueous suspensions was investigated. The 0.06 wt% GO, 0.06 wt% g-C 3 N 4 , and 0.06 wt% 1:1 g-C 3 N 4 /GO suspensions reduced the coefficient of friction (COF) by 37, 26 and 37% and wear mark radius by 19.1, 16.0 and 19.6%, respectively, in comparison with water. Pure g-C 3 N 4 and GO suspensions showed unstable lubrication in the tests with relatively high loads and speeds, while the g-C 3 N 4 /GO mixed suspension had superior tribological performance in all tested conditions. This is because in the mixed suspension g-C 3 N 4 agglomerates became smaller, and GO nanosheets exhibited fewer wrinkles and less stacking, which enabled the formation of a layer of tribo-composite film. As a result, the friction, wear and tribo-corrosion were reduced during sliding.