The structural, electronic, and magnetic properties of bismuth ferrite (BiFeO₃) and Bi₂Fe₄O₉ nanostructures were investigated using Density Functional Theory (DFT) within the Generalized Gradient Approximation (PBE-GGA) plus U approach. The PBE-GGA + U calculations predict band gaps of 2.4 eV for BiFeO₃ and 2.3 eV for Bi₂Fe₄O₉, closely aligning with experimental data. The analysis of partial and total density of states reveals strong hybridization between iron 3d and oxygen 2p states, with a significant contribution from Fe 3d orbitals in both structures. Additionally, nanostructure and crystal symmetry are crucial in influencing the magnetic properties of BiFeO₃ and Bi₂Fe₄O₉. Our calculations indicate that the antiferromagnetic phase is energetically more favorable than the ferromagnetic phase in both materials.