A new complex of the Keggin trilacunary A alpha-PMo9O349-polyoxomolybdate (PMo9) with Fe3+ ions, having the formula A alpha-PFe3III(H2O)(3)Mo9O376- (PFe3Mo9), has been synthesized and characterized by chemical analysis, FT-IR, Raman, UV-VIS-NIR and EPR spectroscopy, as well as by magnetic susceptibility measurements. Cyclic voltammetry performed at different scan rates, pH and supporting electrolyte composition, was used to investigate the electrochemical behaviour of the PFe3Mo9 complex in acidic medium and its electrocatalytic effect on H2O2 reduction. The voltammetric waves were assigned, and the enhanced electrocatalytic efficiency of PFe3Mo9 relative to PMo9 was attributed to the presence of Fe atoms.