Piezo-photochemical water splitting is a promising pathway to achieving sustainable energy. Density functional theory (DFT) approach was used investigate BaTiO3 photocatalysts strategically modified by (Mo + N) and (W + N) co-doping under strain to assess their piezo-photocatalytic performance. Co-doping and strain efficiently regulated electronic structure, band gap, and defect chemistry, improving visible-light absorption and catalytic activity. Hydrogen evolution reactions were favoured by intermediate temperature fluctuations and high carrier mobility. (Mo + N) co-doped BaTiO3 exhibited superior performance with low overpotential and visible absorption up to 401 nm, but efficiency declined under strain due to band gap widening and increased energy barriers. Conversely, (W + N) co-doping maintained stable piezoelectric response and strong absorption across 400–600 nm, effectively balancing strain effects. Optimal strain conditions were 0.00 % for (Mo + N), all ranges for (W + N), and 0.04 % for pure BaTiO3. Overall, strategic co-doping synergistically combined N-induced defects with Mo/W d-orbital states, enhancing carrier mobility and absorption with multiple intensity peaks, better than individual W-, Mo-, or N-doping strategies.