In this paper we report direct electrochemical synthesis of sponge-like MnO2 nanostructures using ultrasonic vibration on the surface of MWCNT modified pencil graphite electrode (PGE). The synthesized nanostructures were characterized by scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDXS) and X-ray fluorescence spectroscopy (XRF). This device was used as a simple and sensitive electrochemical sensor for measurement of Dopamine. The diffusion coefficient (D) and the kinetic parameters such as electron transfer coefficient (α) and ionic exchange current (iex) for Dopamine were also determined using electrochemical approaches. The cyclic voltammetry method showed Dopamine oxidation reaction with an irreversible characteristic and was diffusion-controlled at low scan rates. Using differential pulse voltammetry, the peak current was linearly dependent on Dopamine concentration in the ranges of 0.8–7.0 and 7.0–547.0 µM, with detection limit of 84.9 nM. Finally, DPV was used to quantify of Dopamine in some real samples by the standard addition method. The modified electrode showed good sensitivity and stability by better response than to other reported papers.