NiO/(101)-anatase-TiO2 heterostructure nanoparticles were synthesized by depositing NiO onto the (101) facet of anatase crystals via the supercritical fluid chemical deposition (SFCD) route. Thorough characterization experiments performed by various techniques (XRD, UV-Vis DRS, N2 sorption, HR-TEM, EDX, and XPS) indicate that the SFCD method allowed a good dispersion of NiO onto the TiO2 nanoparticles for NiO amounts below 2 wt%. Compared to pure TiO2, the 0.1–1 wt% NiO–TiO2 nanocomposites showed enhanced photocatalytic properties for methylene blue (MB) and methyl orange (MO) decomposition under UV light irradiation, the 0.25 wt% NiO–TiO2 system leading to the highest efficiencies. The photocatalytic properties were then rationalized in terms of the acidic properties and electronic structures of the NiO–TiO2 nanocomposites. This higher photocatalytic activity was mainly related to the heterocontact at the interface of the NiO–TiO2 crystallites and to the enhanced reaction rates at the NiOx surface.