This paper is focused on the synthesis of gold nanoparticles (AuNPs) using highly branched polyethylenimine (PEI) and acylated polyethylenimine (PEI-C-12) as reducing as well as stabilizing agent and their role as catalysts. The AuNPs are characterized by XRD, TEM, HRTEM, AFM, UV-vis and FT-IR techniques. The AuNPs, in a PEI polyelectrolyte matrix, is found to be a stable and active catalyst for the selective reduction of nitro compounds using NaBH4 under mild reaction conditions. This catalytic system is stable for several months without any obvious colloidal aggregation. (C) 2012 Elsevier B.V. All rights reserved.