In the present study, electrocatalytic oxidation of hydrazine was examined by both cyclic voltammetry and amperometry methods at a disposable, poly(alizarin red S) modified pencil graphite electrode (poly(ALS)/PGE) for the first time. Electrochemical behaviors of both bare PGE and poly(ALS)/PGE were tested by cyclic voltammetry towards 1.0 mM hydrazine in pH 9.0 Britton-Robinson buffer solution. Cyclic voltammograms showed that the oxidation peak potential of hydrazine at PGE (+ 0.70 V) was significantly reduced at poly(ALS)/PGE (+ 0.35 V) and also, a significant increment in oxidation current was observed. The recorded CVs confirmed that poly(ALS) shows high electrocatalytic effect towards oxidation of hydrazine. Secondly, the effects of monomer concentration, cycle number used in electropolymerization step and pH value of supporting solution on oxidation current of hydrazine were also optimized and found to be 1.0 mM, 5 cycle, and pH 10.0, respectively. The designed sensor shows a wide linear response range between 1.0 and 600 mu M hydrazine with a LOD of 0.28 mu M and a sensitivity of 833 mu A mM(-1) cm(-2). The selectivity property of the poly(ALS)/PGE was tested in presence of various interferences. Applicability studies of the poly(ALS)/PGE were also performed on different water samples and high recovery values (95-108%) were obtained.