In the provided study, for the first time, simultaneous electrochemical measurement of Acetaminophen (AC), Tyrosine (Tyr), and Codeine (Cod) was discussed. The CuZnO-Fe3O4/rGO nanocomposite was prepared, then applied for amendment of glassy carbon electrode (GCE) surface in order to measurement of target analytes using differential pulse voltammetry (DPV) technique. Electrical impedance spectroscopy (EIS) techniques displayed that CuZnO-Fe3O4/rGO/GCE has the lowest electron transfer resistance (Rct) in comparison to GCE and was suitable for electrochemical applications. The synthesized compounds were examined using Transmission electron microscopy (TEM), and X-ray Diffraction (XRD). At the CuZnO-Fe3O4/rGO/GCE, three oxidation peaks appeared at 364, 592, and 908 mV with Ipa = 2.41, 2.22 and 2.8 µA for AC, Tyr, and Cod and the peaks separation of ΔEp (AC, Tyr) = 228 mV, and ΔEp (Tyr and Cod) = 316 mV in the potential region 0.0–1.2 V. In optimum DPV condition and pH = 7.0, a dynamic range of AC (0.01–15 and 15–420 µM), Tyr (0.014–18 and 18–460 µM) and Cod (0.01–18 and 18–460 µM) with the detection limit of 6.4, 7.6, and 5.7 nM for AC, Tyr and Cod, respectively, were acquired. The provided sensor was successfully applied for the monitoring of the analytes in urine and human blood plasma spiked samples. The data using the suggested sensor and HPLC method were in good agreement without significant difference.