The electrodeposition of copper- or zinc-based nanomaterials was performed on the top of polypyrrole-polystyrene sulfonate (PPy-PSS) thin films from their respective sulfate solutions in presence of dissolved oxygen. Three main processes were responsible for the formation of the nanomaterials, namely, the capture of Cu2+ or Zn2+ ions by the film from the electrolyte solution, the formation of OH− ions generated from the oxygen reduction reaction, and the reaction of the hydroxide ions with the metal ions to form insoluble double salts. Copper-based hierarchical micro/nanostructure composed of copper hydroxide sulfate hydrate, [CuSO4]2[Cu(OH)2]3·5H2O, and posnjakite, CuSO4[Cu(OH)2]3·H2O, were identified using X-ray diffraction and several other surface analytical techniques. These structures were formed of nanosheets made of nanoparticles which combined into flower-like micro-clusters. The nucleation of the structures was progressive. The morphology and composition of the copper-based materials changed with the deposition potential. Microcrystals and nanosheets were combined using a two-step fabrication procedure to form new hybrid microstructures. Metallic copper nanoparticles (CuNP) were formed from the reduction of the hierarchical micro/nanostructure. The application of a high reduction potential caused the erosion of the nanosheets and the formation of CuNP. These nanoparticles were used to detect nitrate ions. The sensing performance was improved with the introduction of polyethyleneimine-functionalized multiwall carbon nanotubes (MWNT-PEI) to the PPy-PSS films. Electrochemical impedance spectroscopy studies showed that the nanotubes increased the electronic conductivity of the reduced films. The limit of detection of the PPy-PSS-MWNT-PEI-CuNP nanocomposite was 30 µM nitrate. Nanothin sheets made of zinc sulphate hydroxide hydrate, ZnSO4[Zn(OH)2]3·5H2O, were also deposited on the PPy-PSS films and characterized using a range of experimental techniques. The zinc-based sheets formed on the film surface with instantaneous nucleation and grew into a network of entangled nanosheets. The effect of the experimental conditions on the electrodeposition was studied. Interestingly, the formation of the nanosheets was only observed on PPy-PSS films, but not on films doped with other sulfated/sulfonate dopants. The zinc nanosheets were reduced to metallic zinc micro-dendrites and possibly zinc oxide nanocrystals.