A preconcentrating/voltammetric multiwalled carbon nanotube modified glassy carbon electrode (MWCNT–GCE) has been developed for stripping analysis of carbendazim (Methyl Benzimidazol-2-yl Carbamate—MBC), based on dispersing MWCNT in water. The effect of experimental variables, such as the dispersion and loading of MWCNT, was assessed. A quasi-reversible behavior for MBC in acetic acid/acetate buffer 0.1 mol L⁻¹ (pH 4.7) was verified and its high effective pre-concentration was attributed to the high adsorption capability and enormous surface area of the MWCNT. No evidence of carry-over effect, combined with the easiness of electrode preparation, led to the development of a highly sensitive and reliable method with an experimental work range from 0.256 to 3.11 µmol L⁻¹ with a detection limit of 10.5 ppb for a short (60 s) accumulation period. Measurement of MBC in a river water sample was demonstrated. The accuracy of the method for real sample analysis was assessed by estimating the apparent recovery (93 ± 2.9% and 86 ± 4.1% for 4.3 × 10⁻⁷ mol L⁻¹) for a MBC spiked river water sample.