This study introduces a novel approach for synthesizing biomass derived carbon from date leaves waste, employing a straightforward combination of pyrolysis and ball milling processes. This process yields active carbon in submicron and nanometer sizes, characterized by detailed surface, structural, and compositional analyses, confirming suitability of the materials for electrochemical applications. Utilizing this synthesized carbon, we have developed a modified glassy carbon electrode (DLSNC/GCE) for the highly-sensitive and simultaneous detection of phenolic contaminants, specifically 1-naphthol (1-NP) and 2-naphthol (2-NP), which are crucial for environmental monitoring. The study describes two innovative fabrication methods for electrochemical sensors. The first method controls the direct oxidation of 1-NP and 2-NP, while the second method exploits redox peaks associated with quinone formation from dihydroxy naphthalene, revealing superior analytical performance for the simultaneous detection of the analytes. The electrochemical sensor demonstrated exceptional sensitivity and selectivity towards 1-NP and 2-NP. This revolution emphasizes the potential of using date leaves-derived carbon materials in constructing low-cost, efficient electrochemical sensors for environmental monitoring and electrochemical applications.