The green synthesis of ZnO nanoparticles (NPs) was performed using Salvia heldreichiana extract for the first time. The synthesized nanoparticles and their properties on electrode surfaces were characterized by spectroscopic, microscopic and electrochemical techniques. Characterization results showed particle sizes at 35.98 nm (±4.29 nm). Produced ZnO NPs were used to modify the 3D-printed electrodes (3DPE) with and without diallyldimethylammonium chloride (DDA). Modified electrodes were used to determine dopamine electrochemically. A synergistic effect between ZnO NPs and DDA was observed resulting in high sensitivity, a broad linear range and a fit limit of detection 456.84 µA/mM.cm2, 10–8000 µM and 8.56 µM, respectively, via cyclic voltammetry method.