The electrochemical oxidation of HMF (5-hydroxymethylfurfural) to DMF (2,5-furandicarboxaldehyde) catalysed by a salen-manganese homogeneous catalyst is reported. DMF is a versatile precursor in the synthesis of functional polymers, pharmaceuticals, antifungal agents, and furan-urea resins. A manganese(III)-Schiff base complex 1 was synthetized and characterized by different analytical and spectroscopic techniques. Complex 1 behaved as an efficient catalyst of the electrochemical oxidation of HMF to DMF. The conversion of HMF to DFF was performed under mild conditions. The oxidation of DFF to HMF with a conversion rate of 75% was achieved at pH 8.5, using sodium chloride as the electrolyte to increase the conductivity and to reduce the power dissipation.