<p>In this study, a novel electrochemical sensor for the simultaneous trace measurement of dopamine (DA) and tramadol (TR) was created using a glassy carbon electrode modified with multi-walled carbon nanotubes (MWCNTs) and Zn-doped magnetite Fe₃O₄ nanosheets (Zn–Fe₃O₄NS/MWCNTs/GCE). The Fe₃O₄ nanosheets doped with Zn²⁺ were synthesized using the hydrothermal method. Different voltammetric techniques such as cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) were used to investigate the electrochemical behavior of DA and TR. The results demonstrated that the Zn–Fe₃O₄NS/MWCNTs composite exhibited outstanding electro-catalytic activity for the simultaneous measurement of DA and TR. The experimental parameters like buffer type, aggregation time, and PH were optimized. Two linear dynamic ranges were displayed by the sensor under the ideal experimental conditions: 0.05–3 µmol/L and 10–350 µmol/L with a detection limit of 26 nM and 0.05–3 µmol/L and 10–450 µmol/L with a detection limit of 20 nM for DA and TR, respectively. The suggested sensor's suitability for simultaneous investigation of DA and TR in actual samples with considerable recovery was tested using urine and serum samples. The suggested sensor demonstrated commendable stability, strong repeatability, high selectivity, and great sensitivity for determining DA and TR.</p>