Nitrobenzene(NB) is frequently utilized in the production of numerous products and aromatic compounds. Highly toxic nitrobenzene (NB) and its derivatives mix with water resources and cause various serious effects on human health and the environmental ecosystem. It is vital to accurately detect highly dangerous aromatic nitro compounds in the water medium for the sake of safeguarding both human health and environmental safety. Hence, the detection of NB and its derivatives is one focus of electrochemical sensor development. In this work, a sensitive NB sensor has been developed using Ag-CuSe composite. The prepared Ag-CuSe composite modified with a glassy carbon electrode (GCE) has been used for the detection of NB and real sample analysis. In addition, the morphology, crystallinity, and functionality of the Ag-CuSe composite have been determined by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and elemental mapping. The electrocatalytic reduction mechanism and kinetic parameters of the NB at the GCE/Ag-CuSe electrode have been evaluated by cyclic voltammetry, differential pulse voltammetry, and amperometry in 0.05 M phosphate buffer solution (pH 7.0). The GCE/Ag-CuSe-modified electrode exhibited excellent electrochemical activity toward the detection of NB with a low limit of detection (S/N = 3) of 0.01 µM, good sensitivity of 3.64 µA µM−1 cm−2, and a linear response range of 0.1 to 400 µM. Moreover, the Ag-CuSe-modified electrode has excellent selectivity, repeatability, reproducibility, and anti-interference ability, as well as good stability. The prepared GCE/Ag-CuSe electrode has been successfully applied to the removal of pollutants from various real water samples with good recovery results. The proposed GCE/Ag-CuSe electrode has been used for the trace-level detection of nitrobenzene in environmental samples.