This work developed a printed electrochemical sensor for the detection of diuron, a persistent and toxic herbicide, utilizing the screen-printing technique and polyethylene terephthalate (PET) as the support material. The sensor employs a carbon conductive ink composed of graphite (1.875 g), carbon black (0.625 g), and nail polish (2.650 g) for electrode printing. The SPCE sensor was modified with Metallic Nanoparticles (MNP) and characterized using UV-Vis spectroscopy. The modification with gold nanoparticles (AuNPs) increased the electroactive area of the sensor, enhancing its electrochemical performance. The materials used and the fabricated sensor were characterized by Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV). The optimization of experimental conditions, such as the amount of AuNPs used in the modification, pH, and ionic strength of the supporting electrolyte, contributed to an increased sensitivity of the sensor, resulting in a low detection limit (0.15 µmol L-1). The sensor was employed in the determination of diuron, whose presence in aqueous matrices is concerning due to its persistence and toxicity. The SPCE-MNP-Au sensor showed high selectivity in the determination of the herbicide, with a Relative Standard Deviation (RSD) of 4.8%, no matrix effect, and recoveries between 95% and 97.9% in river water samples, allowing us to conclude that the sensor is suitable for the detection of diuron in environmental samples, such as water.