Palladium (Pd) nanoparticles were dispersed on iodinated multi-walled carbon nanotubes (I-MWNTs) by the aqueous solution reduction of Pd(NO3)2 with formaldehyde. The structure and nature of the resulting Pd-MWNT composites were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrocatalytic properties of the Pd-MWNT modified glassy carbon electrode (Pd-MWNT/GCE) for formaldehyde oxidation have been investigated by cyclic voltammetry; high electrocatalytic activity of the Pd-MWNT/GCE can be observed. This may be attributed to the high dispersion of palladium catalysts and the particular properties of MWNT supports. The results imply that the Pd-MWNT composite has good potential applications in fuel cells.