In this work, thin titanium dioxide (TiO2) films were synthesized by atomic layer deposition (ALD) on p-type monocrystalline silicon substrates with planar and nanostructured surfaces. The nanostructured black silicon (b-Si) layer was fabricated using maskless reactive ion etching in an SF6/O2 gas mixture, resulting in an array of conical nanoneedles with high surface area. The structural, optical, and electronic properties of the TiO2/Si and TiO2/b-Si/Si heterostructures were comprehensively characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, as well as current-voltage and spectral responsivity measurements. The results revealed that the ALD TiO2 films crystallize in the anatase phase and provide conformal coverage on both planar and nanostructured surfaces. The b-Si layer increases the ALD TiO2 crystallite size from 31 to 42 nm and reduces the optical reflectance by 4–5 times in the visible and near-infrared ranges. Electrical measurements demonstrated enhanced photocurrent and a shift in the spectral responsivity maximum to the visible region (up to 0.28 A/W at 500–600 nm) for TiO2/b-Si/Si heterostructures, attributed to improved light absorption and increased contact area. However, the nanostructured b-Si layer also leads to a higher reverse current and a decrease in the potential barrier height from 0.83 to 0.68 eV, indicating the need for nanostructure optimization to minimize recombination losses. These findings highlight the potential of TiO2/b-Si/Si heterostructures for high-efficiency optoelectronic devices, including solar cells and broadband photodetectors.