It has been shown that a cationic copolymer based on poly(aminoethyl methacrylate) is capable of stabilizing silver nanoparticle dispersions in aqueous media. Nanoparticles have been prepared via chemical reduction of AgNO3 in an aqueous solution with sodium borohydride in the presence of a cationic random terpolymerpoly(2-aminoethyl methacrylate-co-N-methyl-2-aminoethyl methacrylate-co-N,N-dimethyl-2-aminoethyl methacrylate). Spectrophotometry has been employed to show that silver dispersions formed in the presence of the copolymer are stable for a long time (more than half a year). Using dynamic light scattering and scanning electron microscopy, consistent information has been obtained on the sizes and size distribution of the stabilized nanoparticles.