Copper nanoparticles were fabricated in poly(vinyl alcohol)/polyacrylamide interpenetrating polymer networks (PVA/PAAm IPNs) by reduction of copper ions with sodium hypophosphite in aqueous solutions. The PVA/PAAm IPNs hydrogels were synthesized in terms of a simultaneous interpenetrating route in the presence of glutaraldehyde and N,N'-methylene-bis-acrylamide. The swelling and mechanical properties of the resulting PVA/PAAm/Cu nanocomposite hydrogels were investigated by a gravimetric method and compression stress-strain test. The results indicated that the copper nanoparticles were assembled in the PVA/PAAm IPN hydrogels in a spherical shape, and were well dispersed and stabilized by the polymer networks, with a size range from 10 to 20 nm. The complexation of PVA and PAAm with Cu2+ in PVA/PAAm IPNs played an important part in avoiding the aggregation of copper nanoparticles, and providing particle size and size distribution controllability and stability. The nanocomposite hydrogels exhibited slightly lower swelling, but better compression mechanical properties than that of the control PVA/PAAm IPNs. These properties can be easily tuned by changing the component ratios to meet the requirements of the specific applications such as drug controlled release or tissue engineering.