The growing emphasis on green energy has spurred momentum in research and development within the field of photocatalytic materials, particularly for green hydrogen production. Among the most abundant oxides on Earth, oxychalcogenides stand out for their cost-effectiveness and ease of synthesis. In this context, we present an investigation of the potential use of BiAgOS as an efficient photocatalyst for hydrogen generation. Utilizing density functional theory and ab initio molecular dynamics (AIMD) simulations, we computed its physical properties and assessed its photocatalytic performance. Specifically, using Heyd–Scuseria–Ernzerhof corrections, our calculations yielded an appropriate electronic gap of ~1.47 eV necessary for driving the water-splitting reaction. Additionally, we obtained a very high optical absorption coefficient of ~5 × 105/cm–1 and an estimation of hydrogen generation yield of ~289.56 µmol∙g–1. These findings suggest that BiAgOS holds promise for enabling the development of cheap, reliable, and highly efficient photocatalysts for hydrogen production.