The objectives of this DFT study are to consider the adsorption properties of the 4-[2-[4-(dimethylamino) phenyl] diazenyl]-benzoic acid (p-methyl red) dye molecule on the pristine B3O3 semiconducting layer for potential application in dye-sensitized solar cells. Adsorption of dye molecules on different positions of the B3O3 nanosheet leads to the formation of the complexes with favorable adsorption energy in the range of -0.25 to -1.48 eV and the 50 to 57% percentage of change in band gap energy of the monolayer. The dye molecule is adsorbed in two forms on the B3O3 surface, the complexes of the trans-isomer with a more negative adsorption energy of -1.48 eV being more stable than -1.41 eV of the cis-isomer complexes. By the adsorption of dye molecules on the pristine B3O3 surface, the electronic properties of the surface change a lot, which in this work can be proved with the percentage of the changes in the gap energy of more than 50%. The present study results show that the studied substrate may be suitable for application in dyesensitized solar cells via pairing with a desired dye molecule.