For the first time, a glassy carbon electrode (GCE) with decorated gold nanoparticles (nanogold electrode: NGE) was applied as an underlying substrate for template-free electropolymerisation of pyrrole (Py). The principal aim of this study was to investigate synergic effects of NGE and polypyrrole (PPy) on electrochemical responses. Effects of fabrication conditions (Py concentration and the number of scan cycles) on PPy film morphology and current responses were emphasised. Immobilisation of horseradish peroxidase (HRP) was concomitantly achieved with electropolymerisation of Py that completed a modified electrode for the amperometric detection of phenol, a model analyte. A NGE/HRP/polypyrrole (PPy) biosensor resulted in a 4.5-fold higher current response in comparison with that of a GCE/HRP/PPy. A synergy between AuNPs (of the NGE) and PPy was suggested. The initial Py concentration and a number of scan cycles for polymerisation were found to be the governing parameters for electrode surface morphology and electrochemical responses. Scanning electron micrographs revealed formation of homogeneous PPy nanorods under certain electropolymerisation conditions. Optimum conditions were determined at an initial Py concentration of 0.09 M and 10 cycling numbers. NGE could certainly be applied as an underlying substrate for other enzyme/polymer or sole polymer matrices for detection of other analytes in biosensors and chemical sensors.