Recent advancements in experimental approaches have made it possible to synthesize silver (Ag5) atomic quantum clusters (AQCs), which have shown a great potential in photocatalysis. This study employs the generalized gradient approximation (GGA) density functional theory (DFT) to explore the adsorption of CO2, CH4, and H2O molecules on the Ag5 AQC. Our investigations focus on the structural and electronic properties of the molecules in Ag5 AQC systems. This involves adsorption energy simulations, charge transfer, charge density difference, and the density of states for the modelled systems. Our simulations suggest that CH4 and H2O molecules exhibit higher adsorption energies on the Ag5 AQC compared to CO2 molecules. Remarkably, the presence of CH4 molecule leads to a significant deformation in the Ag5 AQC structure. The structure reforms from a bipyramidal to trapezoidal shape. This study also reveals that the Ag5 AQC donates electrons to CO2 and CH4 molecules, resulting in an oxidation state. In contrast, gaining charges from H2O molecules results in a reduced state. We believe the proposed predictions provide valuable insights for future experimental investigations of the interaction behaviour between carbon dioxide, methane, water molecules, and Ag5 sub-nanometre clusters.