Numerical models based on DFT and semi-empirical methods were developed on bulk and nano-sized BiVO₄ semiconducting oxide. Two different approaches were implemented to calculate the electronic properties of the bulk BiVO₄ crystal. One approach used the X-ray specified atomic positions with the defined lattice parameters involved in the monoclinic crystalline structure of BiVO₄, for which geometry optimization was performed before the electronic properties calculations. The second approach considered the atomic positions of the scheelite structure, which was maintained frozen without any lattice rearrangement. The obtained data were considered as a guideline to choose appropriate methodology to calculate the physical properties of (BiVO₄)_n nanoparticles. A semi-empirical method with the PM6 parameterization was applied to calculate the electronic and vibrational properties of (BiVO₄)_n nanostructures versus their sizes. The quantum confinement effect was shown for the clusters through a blue-shift of the optical absorption bands compared to an infinite system. It was demonstrated that the optical and vibrational properties of the nanoparticles are determined by the internal atoms keeping their positions as in the crystalline structure and also that they feel surface reconstruction effects according to the environmental interactions. The above mentioned behaviors were analyzed (using UV-vis absorption, IR and Raman features), theoretically predicted and then compared with the experimental results. The performed analyses underlines the evolution of the electronic density of states and the optical absorption peculiarities between a bulk infinite system and nano-sized objects dedicated to realize visible-light-driven photocatalysts.