<p>Dopamine is a chemical messenger that plays a vital role in normal human physiology. However, an abnormal amount of dopamine is connected to an increased risk of neurological diseases. Here we report a new, inexpensive, and rapid colorimetric method based on the deposition of manganese oxide nanoparticles over biocompatible and biodegradable banana peel powder (MnO₂@bpp) for the detection of dopamine. The synthesized nanocomposite was characterized using spectroscopic, morphological, and surface chemical state-determining techniques. The synthesized nanocomposite (MnO₂@bpp) was used as a mimic enzyme for the detection of dopamine visualized by tetramethylbenzidine (TMB- chromogenic substrate) without the use of H₂O₂. The various parameters affecting the efficiency of the proposed sensor, such as the amount of the nanozyme, pH, concentration of TMB, and time, were optimized for the detection of dopamine. Excellent linearity was obtained for the quantitative determination of dopamine in the range of 1 to 60 µM. The method is quite sensitive, as indicated by its low limit of detection of 0.13 µM and a limit of quantification of 0.43 µM with an R² value of 0.994. In the presence of many possible interfering species, the designed sensor exhibited good selectivity. The developed sensor was used to detect dopamine in urine samples within the assay’s linear range.</p>