The electrochemical detection of p-nitrophenol (PNP) has gained significant attention due to its potential application in environmental monitoring and food safety. In this study, a novel electrochemical sensor based on a (CeGdHfPrZr)O2 (HEO) nanoparticle-modified glassy carbon electrode (GCE) has been developed for the detection of PNP. Hydrothermal synthesis was employed to prepare a single-phase HEO nanoparticle. Various characterization techniques were employed to investigate the prepared HEO nanoparticles. The GCE was modified with HEO nanoparticles to enhance its electrocatalytic activity for the detection of PNP. As a result, the oxidation peak current of PNP was greatly enhanced compared to unmodified GCE, indicating an improved electrode reaction kinetics. The sensor showed high sensitivity (0.1517 μA μM−1 cm−2) and selectivity towards PNP, with a detection limit as low as 0.321 μM. The developed electrochemical sensor exhibited excellent reproducibility and selectivity towards PNP over other interfering species. The reusability and stability of the sensor were also investigated. The modified GCE exhibited good long-term stability and could be reused for at least 50 cycles without significant loss of sensitivity