This research in finding a cheap and efficient catalyst for electrooxidation of formaldehyde give Lis an attempt to make and examine the behavior of poly(N-methylaniline)/nickel modified carbon paste electrode (Ni/P(NMA)/MCPE) in absence and presence of formaldehyde. This involves ill situ electropolymerization of N-methylaniline at carbon paste electrode, which is following to the incorporation of Ni(II) to polymeric layer by immersion of modified electrode in 1.0 M nickel sulphate Solution. The electrocatalyric oxidation of formaldehyde was studied by cyclic voltammetry and chronoamperometry methods. The effects of scan rate and formaldehyde concentration on the electrocatalytic oxidation of formaldehyde were also investigated at the surface of Ni/P(NMA)/MCPE. The diffusion coefficient (D = 14.1 x 10(-5) cm(2) s(-1)), and some kinetic parameters such as the transfer coefficient (alpha = 0.45) and also second-order rate constant (k = 8.96 x 10(-4) cm(3) mol(-1) s(-1)) of formaldehyde were calculated. (C) 2009 Elsevier B.V. All rights reserved.