One-step E-Coli bacterial assisted method was employed to synthesize Cadmium Sulfide/reduced graphene oxide (CdS/rGO) nanocomposite and its photocatalytic Hydrogen production activity was studied under visible light irradiation. The loading of rGO in nanocomposite was varied to study its effect on photocatalytic Hydrogen production. Among all, CdS/rGO (2 wt%) showed highest photocatalytic activity i.e. it produced 500 mu molg(-1) of Hydrogen. The enhanced photocatalytic activity of CdS/rGO (2 wt%) was due to decrease in its work function to 3.98 eV and good efficiency in the separation of photogenerated charge colliers, which in turn indicate the increased lifetime of charge carriers. Furthermore, the CdS/rGO (2 wt%) nanocomposite showed excellent photocatalytic stability for Hydrogen production due to the presence of rGO, which protects the CdS nanoparticles from photo-corrosion. It is anticipated that this work could enhance the information on photo catalytic mechanism of CdS/rGO nanocomposite towards Hydrogen production under visible light irradiation.