The electrochemical behaviors of an emerging pollutant, benzotriazole (BTA), at multiwall carbon nanotubes and Nafion modified glassy carbon electrode (MWNTsNafion/GCE) were investigated systematically. The electrochemical reduction of BTA was significantly improved by MWNTs-Nafion compared to bare GCE, ascribed to the excellent adsorption capacity and electrocatalytic activity of MWNTs. BTA presented well-defined reduction peaks only at pH <3.0, suggesting the involvement of lots of protons in the reduction process. Peak potential shifted negatively and peak current decreased significantly with pH increase. BTA showed various UV-Vis absorption spectra in acidic and alkaline mediums. Cathodic peak current increased linearly with square root of sweep rate as well as with the concentration of BTA from 3.0 × 10 −6 to 1.6 × 10 −4 mol L −1 . This suggests a diffusion-controlled and irreversible electrode process.Diffusion coefficient of BTA on MWNTs-Nafion/GCE was obtained as 2.67 × 10 −2 cm 2 s −1 with four orders of magnitude larger than that on GCE. MWNTs-Nafion/GCE showed a good selectivity between BTA and O 2 but poor selectivity between BTA and tolyltriazole.