Dendrimers have shown as a promising candidate in controlling the size, shape and avoid agglomeration of the metal nanoparticles. Platinum nanoparticles are stabilized by fourth generation amine terminated poly(amidoamine) (G4-PAMAM) dendrimers and anchored successively onto carbon by two methods, namely ester functionalization (Pt-DENs/C_est) and active anhydride functionalization (Pt-DENs/C_anh) as the cathode catalyst in polymer electrolyte membrane fuel cells (PEMFCs). The effects of pH and reaction time on the complexation reaction are examined by the UV-vis spectroscopic technique. The electronic and structural features of nanoparticles are studied by X-ray photoelectron spectroscopy (XPS), the X-ray diffraction technique (XRD) and Transmission Electron Microscopy (TEM). Electrochemical behaviour and catalytic activity of the catalysts are studied by cyclic voltammograms (CV) and linear sweep voltammograms (LSV) in N₂ and O₂ saturated 0.1 M aqueous HClO₄. Effect of functionalization is studied and a significant result has been observed. The PEMFC performance of the catalysts synthesized using the dendrimer was compared with the catalyst without the dendrimer. Pt-DENs/C_anh show significant performance over Pt/C prepared in the absence of the dendrimer.