A simple, single pot synthesis method has been described for the synthesis of AuAg alloy nanoparticles using cationic long chain polymer. Unlike other methods for alloy NP synthesis, our method is unique because of its fast synthesis rate and robust nature. The high stability of the synthesized monometallic and bimetallic nanoparticles is attributed to the combined effect of the steric hindrance and electrostatic repulsion provided by polymeric stabilizer. Efficient reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of alloy nanoparticles and NaBH4 is investigated and is found to depend upon the gold content in the nanoparticles.