In this work, spherical Pt nanometer-scale particles supported on the poly (m-toluidine)/Triton X-100 film modified carbon nanotube paste electrode (Pt/PMT (TX-100)/MCNTPE) was used as a potent catalyst for electrooxidation of formaldehyde (HCHO) in both 0.5 M H2SO4 and 0.1 M NaOH solutions. The obtained results showed that utilization of TX-100 as an additive during the electropolymerization process enhances the electrocatalytic activity of the modified electrode towards HCHO oxidation. The onset potential of HCHO oxidation was shifted in 0.1M NaOH to less positive values than that of the acid solution which is due to the solution pH. Then, the influences of some parameters such as potential sweep rates, switching potential, and HCHO concentration on its oxidation have been investigated to provide the first insight into the electrooxidation behavior of HCHO in the alkaline medium. Also, stability of the modified electrode was examined by potential cycling in both acidic and alkaline solutions and the obtained results showed that in 0.1 M NaOH solution, a sufficient improvement was noted. The present study shows a promising choice of the Pt/PMT (TX-100)/MCNTPE as composite catalyst for HCHO oxidation at a reasonable low overpotentials.