Direct production of hydrogen from photocatalytic water splitting is a potential solution to overcome global energy crisis. Herein, based on first-principles calculations, we demonstrate that the two-dimensional β-PdSe₂ monolayer is a promising candidate for efficient photocatalytic water splitting in acidic and alkaline media as well as neutral medium with highly efficient solar-to-hydrogen efficiency. β-PdSe₂ monolayer shows low cleavage energy which endorses the possibility of its mechanical exfoliation from layered bulk β-PdSe₂. Remarkably, β-PdSe₂ monolayer is semiconducting with indirect band gap of 1.96 eV with perfect engulfing the redox potential of water in a wide range of pH of medium. β-PdSe₂ monolayer exhibits good light harvesting ability and adequate driving forces for water redox reaction in wide range of pH (0 to 12). Comprehensive investigation of pH dependent water splitting indicates that the β-PdSe₂ monolayer is a better candidate for efficient water splitting in alkaline media rather than acidic or neutral medium. In addition, high solar-to-hydrogen efficiency as high as ∼17% is obtained that shows β-PdSe₂ monolayer a promising candidate for overall photocatalytic water-splitting.