In this contribution we describe the formation of gold nanoparticles (AuNP) and polyaniline (PANI) AuNP-PANI nanocomposite via in situ enzymatic polymerization. The method consists of electrostatic adsorption of anilinium monomers on AuNPs citrate stabilized surface of 50 nm diameters, followed by oxidation with horseradish peroxidase (HRP) enzyme and its cofactor H 2 O 2. All reaction steps were monitored by UV-Vis-NIR spectroscopy including in situ detection of the polymerization process. UV-Vis-NIR, Cyclic voltammetry (CV) and surface enhanced Raman scattering (SERS) measurements supported the formation of a nanoshell of PANI on the AuNP core.