In this study, BaSnO3 thin films were grown on MgO substrates by pulsed laser deposition, and their structural, optical, and electronic properties were investigated by combining experiment and first-principles calculations. X-ray diffraction confirmed the preferentially oriented growth of BaSnO3 films without detectable secondary phases. UV–Vis spectroscopy and Tauc analysis yielded indirect and direct optical bandgaps of approximately 3.15 eV and 3.6 eV, respectively. Density functional theory calculations were performed using the ABACUS package with both LCAO and plane-wave basis sets. The indirect and direct bandgaps were compared for PBE, HSE, PBE0, DDPBE0, and DSR functionals. PBE and HSE underestimated the bandgap, whereas DDPBE0 and DSR provided values closer to the experimental optical gap. The LCAO calculations reproduced the overall functional dependence observed in plane-wave calculations but generally predicted smaller bandgaps, which is attributed to the limited description of the delocalized Sn 5s-derived conduction band by localized numerical atomic orbitals. These results highlight the importance of both hybrid functional selection and basis-set effects in accurately predicting the electronic structure of BaSnO3.