Samarium oxide (Sm₂O₃), such as electrochemical sensors, is a promising material in various application prospects and industries. Additionally, Sm₂O₃ leverages electron transport capabilities, high electrical conductivity, and thermal stability to develop an effective material in electrode modification for detecting hazardous pollutants. Hydrazine and p-nitrophenol are compounds commonly used in producing insecticides, pesticides, pharmaceuticals, and the chemical industry. However, these compounds can become hazardous environmental pollutants and pose serious health risks to humans. Therefore, this research aims to examine the impact of modifying gold electrode (GE) with Sm₂O₃ nanoparticles, characterizing the electrochemical results, and assessing sensor performance through the use of the GE/Sm₂O₃ NP electrode. In this context, the purpose is to detect hydrazine and p-nitrophenol through voltammetry, with analytical parameters including recovery, repeatability, detection limit, quantification limit, and linear range. The results show that the synthesis of Sm₂O₃ nanoparticles and the performance of the sensor and analytical parameters of GE/Sm₂O₃ NP are carried out in detecting hydrazine and p-nitrophenol using the Cyclic Voltammetry (CV) method. Furthermore, the significant increase in the current response validates the improvement of GE conductivity as an electron transporter. The sensor performance has been studied, and analytical parameters have been determined. For hydrazine and p-nitrophenol, the values are recovery of 98.74 % and 99.01 %, repeatability of 99.42 % and 98.45 %, limit of detection (LoD) of 0.4684 μM and 0.50332 μM, limit of quantification (LoQ) of 1.4194 μM and 1.5252 μM, and linear concentration range for both analytes from 0.1 μM to 7 μM.