The present work describes an electrochemical detection of nitrite by using screen-printed carbon electrode (SPCE) modified manganese dioxide@graphitic carbon nitride nanocomposite (MnO2@g-C3N4). The MnO2@g-C3N4 nanocomposite was successfully prepared by a facile low-temperature hydrothermal process and characterized using XRD, FT-IR, N-2 adsorption-desorption isotherm, XPS, FE-SEM, HR-TEM, and EIS. The nanocomposite exhibited excellent synergistic effect and enhanced electrocatalytic activity than electrodes modified with MnO2 and g-C3N4. In comparison to cyclic voltammetry (CV) results of bare SPCE and modified SPCEs, the large electrochemical current difference was achieved in MnO2@g-C3N4 nanocomposite electrode for nitrite detection. The differential pulse voltammetry was used to determine the nitrite and the voltammetric response of nitrite was linear over the 0.01-1520 mu M with a low detection limit (LOD) of 1.23 nM (S/N = 3) and high sensitivity of 24.1777 mu A mu M-1 cm(-2), which are much better than the results reported so far for electrochemical nitrite detection. The MnO2@g-C3N4 nanocomposite electrode also revealed high selectivity of nitrite detection in the presence of potentially interfering compounds even in high concentration. As proof of this method, the practicability of the sensors was examined in tap water, drinking water and rotten beef samples and revealed acceptable recovery for the determination of nitrite. (C) 2019 The Electrochemical Society.