Fine particles of Ayous sawdust (AS) were successfully modified by maleic anhydride to increase their accumulation capability towards carbendazim (Cbz) and used to modify glassy carbon electrode (GCE) for the detection of this pesticide. For a more efficient use of the biosourced material as electrode modifier for electrochemical detection, the functionalized particles were mixed with carbon nanotubes to yield a conductive composite. After characterization by cyclic voltammetry and electrochemical impedance spectroscopy, the modified GCE was applied to Cbz detection. A sensitivity of (2.61 ± 0.08) μA M-1 and a detection limit of 0.04 μM were determined under optimized experimental conditions. Moreover, the designed sensor was found efficient for Cbz determination in real samples (spring water and commercial pesticide product).