We have described the fabrication of high-performance amperometric sensors derived from graphene oxide–multiwalled carbon nanotube (GO–MWCNT) composite for the sensitive determination of diuron and fenuron. GO–MWCNT composite was prepared by simple solution-based approach, and its formation was confirmed by scanning electron microscopy, transmission electron microscopy and UV-visible spectroscopy methods. GO–MWCNT film-modified glassy carbon electrode exhibited excellent electrocatalytic performance in the oxidation of diuron and fenuron in terms of less overpotential and highly enhanced peak currents. GO–MWCNTs have presented significantly improved electrocatalytic performance than dimethylformamide-dispersed MWCNTs. GO–MWCNT-based amperometric sensor has been fabricated which detects diuron in wide linear range between 9 μM and 0.38 mM with high sensitivity of 0.645 μA μM−1 cm−2. The amperometric sensor also detects fenuron in broad linear range between 0.9 and 47 μM with sensitivity of 1.20 μA μM−1 cm−2. Moreover, the sensor offers appreciable repeatability, reproducibility, and stability results. Practical feasibility of the prepared amperometric sensor has been assessed in various water samples collected from agricultural areas.