Copper nanoparticles were synthesized using generation 4 hydroxyl-terminated (G4-OH) poly(amidoamine) (PAMAM) dendrimers as templates. The synthesis is conducted by coordinating copper ions with the interior amines of the dendrimer, followed by chemical reduction to form dendrimer-encapsulated copper nanoparticles (Cu-DEN). The catalytic activities of Cu-DEN were assessed using a model reaction involving the reduction of p-nitrophenol to p-aminophenol with sodium borohydride. The rate constant for the catalytic activity was estimated by measuring the pseudo first-order reaction kinetics obtained by monitoring time-dependent absorbance changes of p-nitrophenol reduction at 400 nm using UV-vis spectroscopy. (Contains 4 figures and 1 scheme.)