Poly(vinylpyrrolidone) (PVP) is a polymer capable of complexing and stabilizing Ag and Au nanoparticles formed through the reduction of Ag+ or AuCl4- ions with N,N-dimethylformamide. The reduction can be efficiently performed both at reflux and under microwave irradiation, but each of these methods leads to different nanoparticle morphology and colloid stability. The use of microwave irradiation provides an extra degree of control of the reduction process. The use of PVP with different polymer chain lengths leads to particles with similar sizes though with a different degree of stability. The colloids are also stable in ethanol for months, but only marginally stable in water.