An electrochemical sensor using a novel three dimensional (3D) ternary Pt nanodendrite/reduced graphene oxide/MnO₂ nanoflower (Pt/RGO/MnO₂) modified glassy carbon electrode was proposed for the selective and sensitive determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to evaluate electrochemical behaviors of DA on the as-prepared electrode. The oxidation peak current of DA is linearly proportional to its concentration in the range from 1.5–215.56 μM, with a detection limit of 0.1 μM (at S/N = 3). Compared to bare RGO, Pt nanodendrite/RGO and MnO₂ nanoflower modified electrodes, the 3D hierarchical ternary Pt/RGO/MnO₂ composites displayed the highest electrocatalytic activity for the selective detection of DA. Moreover, the 3D Pt/RGO/MnO₂ modified electrode can be reused with no obvious deterioration in the electrocatalytic performance. This work paves the way for developing a novel 3D nanostructure and offers new opportunities for improving the performance of electrochemical sensors with excellent sensitivity, repeatability and anti-interference.