<p>Developing selective and sensitive methods for uranium monitoring is crucial for environmental safety and public health. In this study, we report the functionalization of boron-doped diamond (BDD) microcell electrodes using diazonium salt chemistry, followed by grafting of the nitrilotriacetic acid (NTA) ligand to enable the electrochemical detection of hexavalent uranium (U(VI)). Key parameters, including the number of diazonium cycles, pH, and electrolyte composition, were optimized to enhance the sensor’s performance. The surface modification steps were confirmed through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), contact angle measurements, and surface energy analysis. Upon exposure to U(VI)-containing solutions, the modified electrode demonstrated a linear electrochemical response over a concentration range of 8.5 × 10⁻¹² to 4.5 × 10⁻⁶ M, with a detection limit as low as 4&#xa0;pM, highlighting then the high sensitivity of the sensor. Notably, the sensor exhibited excellent selectivity for U(VI) in the presence of common interfering metal ions such as Zn(II), Cd(II), Pb(II), and Cu(II) and against different anionic and organic compounds. The sensor’s practical applicability was further validated through uranium detection in real water samples, with results closely matching those obtained by inductively coupled plasma mass spectrometry (ICP-MS). These findings confirm the sensor's reliability and potential for accurate, on-site uranium monitoring in environmental matrices.</p>