A stable gel of Au nanoparticles in polydimethylsiloxane (PDMS) nanocomposite is prepared by employing the curing agent of PDMS elastomer as a reducing agent for the formation of Au nanoparticles by an in-situ process. The viscoelastic nature of these gels is very sensitive to the Au nanoparticle loading and the synthetic temperature conditions. Even a very low Au content of 0.09 wt% is sufficient enough to bring in the transition from sponge state to gel state at room temperature. Higher synthetic temperature also forms sponge formation. Infrared and ultraviolet-visible spectroscopy measurements have provided insight into PDMS crosslinking and nanoparticle formation, respectively. The optimization of the gel properties can have direct influence on the processability of Au nanoparticle-PDMS nanocomposite gels, with interesting implications in electronic, optical and microfluidic devices. © Indian Academy of Sciences.