The biggest bottleneck restricting the application of two-dimensional (2D) g-C3N4 material in water lubrication is the large-scale acquisition of g-C3N4 nanosheets with satisfactory water dispersibility. In this work, a gel-like g-C3N4 nanosheet hybrid with g-C3N4 nanosheet cores and organic shells was constructed from the bulk g-C3N4 by three procedures of Hummer’s exfoliation, sulfonation, and acid–base neutralization. The hybrid in water exhibited nice water dispersibility and superior tribological performance. Adding 8 wt % of g-C3N4 nanosheet hybrid made the friction coefficient and wear volume of water reduce by 73.7 and 72.3%, respectively. Moreover, its load-carrying capacity under high load and durability under a long-term test were also impressive. The worn surface analyses reflected that a thick protective lubrication film (>150 nm) was distinctly formed on the surface lubricated by the hybrid aqueous dispersion. This film was actually a tribofilm composed of amorphous tribochemical reaction products (FexOy, FexSy, and Fex(SO4)y) embedded with FexOy and g-C3N4 nanocrystals, which not only remarkably reduced the friction and wear but also effectively restrained the oxidation and corrosion of the friction pair. Given the possibility of large-scale construction and the prominent tribological performance, the g-C3N4 nanosheet hybrid is a promising candidate to be developed as a particularly promising water-based additive.