A novel electrochemical immunosensor for highly sensitive detection of deoxynivalenol (DON) in food samples was successfully developed based on single-walled carbon nanotubes/chitosan. The principle was based on the indirect competition between anti-DON, free DON and DON-bovine serum albumin on a glassy carbon electrode modified by the functionalized nanotube/chitosan films. Anti-rabbit immunoglobulin G secondary antibody labelled with alkaline phosphatase was used to react with primary antibody. Differential pulse voltammetry signal could be generated from the hydrolysis of substrate alpha-naphthyl phosphate catalysed by alkaline phosphatase. The electrochemical signal was linear with the logarithm of DON concentrations, ranging from 0.01 to 1000 ng mL(-1) with a detection limit of 5 pg mL(-1) under optimal conditions. In addition, the designed strategy was successfully applied to assay DON in different kinds of food samples, showing satisfactory recovery and consistency with high-performance liquid chromatography. [GRAPHICS]