A transition metal oxide, MnO₂, doped reduced graphene oxide (rGO) was prepared to develop a 2D-carbon-metal oxide composite modified glassy carbon electrode (GC) for sensitive electrochemical determination of nitrite ion (NO₂⁻). GO was first synthesized and reduced to rGO followed by a MnO₂ doping process. The obtained MnO₂-rGO composite was then characterized with Raman spectroscopy, infrared spectroscopy, and scanning electron microscopy techniques. The MnO₂-rGO coated on GC electrodes were electrochemically characterized using cyclic voltammetry, electrochemical impedance spectroscopy and optimized for the determination of NO₂⁻ using differential pulse voltammetry. A linear calibration curve was obtained between 0.1 and 5.5 μM with LOD and LOQ values of 0.02 μM and 0.06 μM, respectively. The selectivity of the proposed sensor was tested in different substances and no significant interference was found. The sensor validation test showed that the precision (% RSD) and accuracy of the system were around 1.95–2.73% and (− 3.5)–2.5%, respectively. Finally, real sample tests with commercially available juice samples and tap water confirmed that the method could detect the spiked NO₂⁻ in real samples. As a result, the sensitive and easy determination of NO₂⁻ has been achieved using MnO₂-rGO composite materials in real samples with good recovery values and minimum interference.