A TiO₂ heterostructure modified with carbon nitride nanosheets (CN-NSs) has been synthesized via a direct interfacial assembly strategy. The CN-NSs, which have a unique two-dimensional structure, were favorable for supporting TiO₂ nanoparticles (NPs). The uniform dispersion of TiO₂ NPs on the surface of the CN-NSs creates sufficient interfacial contact at their nanojunctions, as was confirmed by electron microscopy analyses. In comparison with other reported metal oxide/CN composites, the strong interactions of the ultrathin CN-NSs layers with the TiO₂ nanoparticles restrain their re-stacking, which results in a large specific surface area of 234.0 m²·g^-1. The results indicate that the optimized TiO₂/CN-NSs hybrid exhibits remarkably enhanced photocatalytic efficiency for dye degradation (with k of 0.167 min^-1 under full spectrum) and H₂ production (with apparent quantum yield = 38.4% for λ = 400 ± 15 nm monochromatic light). This can be ascribed to the improved surface area and quantum efficiency of the hybrid, with a controlled ratio that reaches the appropriate balance between producing sufficient nanojunctions and absorbing enough photons. Furthermore, based on the identification of the main active species for photodegradation, and the confirmation of active sites for H₂ evolution, the charge transfer pathway across the TiO₂/CN-NSs interface under simulated solar light is proposed.