Photocatalytic water splitting has emerged as a key approach to sustainable hydrogen production, yet many photocatalysts suffer from limited solar absorption and low conversion efficiency. In this study, we investigate the electronic, optical, and photocatalytic characteristics of SrTaO through density functional theory (DFT) calculations, utilizing the generalized gradient approximation (GGA) for the exchange-correlation potential. The findings show that SrTaO primarily absorbs ultraviolet (UV) light, which limits its photocatalytic activity to the UV range. To enhance its photocatalytic performance, we explore vanadium(v) doping in Tantalum (Ta) sites and the introduction of oxygen vacancies (OVs). The results demonstrate a significant improvement in photocatalytic performance, with hydrogen production rates increasing from 2.18 μmol g for pure SrTaO to 259.8 μmol g for V-doped SrTaO with oxygen defects. Furthermore, the quantum efficiency (QE) and solar-to-hydrogen (STH) conversion efficiency improve notably, with the STH efficiency reaching 17.1%. These modifications help overcome light-harvesting limitations and contribute valuable insights toward the development of more effective photocatalysts for solar-driven hydrogen production.