Electrocatalytic hydrazine oxidation was studied by using a glassy carbon electrode coated with monomeric and polymeric Fe-tetraaminophthalocyanine. The polymeric complex-modified electrode is a better catalyst than the monomer-modified electrode. It presents higher activity at lower potentials and a very good reproducibility. A linear correlation between I,, and hydrazine concentration in a wide range, from 1 x 10(-6) to 1 x 10(-2) M at pH 13 for the polymer-modified electrode was obtained. The open circuit measurements for the polymer-modified electrode in aqueous solution in both presence and absence of hydrazine show that an electronic transfer occurs without an applied potential, from the hydrazine to the Fe (II) metal center. The kinetic electro-oxidation parameters for the polymer-modified electrode were investigated and a probable mechanism operating at pH 13 is proposed.