A selective, sensitive, quickly responsive and simple sensor for methyl parathion (MP) detection was developed using a composite based on a nearly 45% by weight of highly dispersed multiwalled carbon nanotubes (MWCNT) in a zirconia matrix, synthesized by sol-gel method. The composite MWCNT/zirconia showed a mesoporous nature, presenting a high surface area of 135 m2 g−1, where morphology and texture of MWCNT were preserved. The modified carbon paste electrode, obtained with this porous composite, presented an electroactive area of 7.4 mm2, showing a good response for MP detection. The electrochemical parameters for MP were obtained by differential pulse voltammetry (DPV) with detection limit of 9.0 × 10−9 mol L−1 and sensitivity of 1.475 μA μmol−1 L in a linear interval of 19.9 × 10−6 at 176.8 × 10−6 mol L−1. The electrode presented good selectivity in the presence of different interferences; it also showed good repeatability with RDS 0.91% for 13 cycles and reproducibility with RSD 14.2% in measurements. The sensing platform was tested in an ethanolic soybean extract with addition of methyl parathion at concentrations of 160; 180 and 200 × 10−6 mol L−1. The recoveries varied from 102 to 113%, and the relative standard deviation was 5.2%. The developed sensor demonstrated to be adequate for its utilization in the determination of methyl parathion with the purpose to ensure food safety.