Abstract: A sensitive electrochemical sensor for dopamine (DA) determination was developed using electrochemically polymerized L-tryptophan on graphene-coated glassy carbon (GC) as the electrode. The composite electrode showed an excellent electrochemical catalytic activity towards DA oxidation. The peak oxidation current, recorded by differential pulse voltammetry, is logarithmically proportional to the DA concentration from 0.2 to 100 μM. The electrode has a high detection selectivity in the presence of a high concentration of ascorbic acid and a low detection limit of 0.06 μM, which has been used for DA detection in real samples. The success of the sensor in DA detection is ascribed to a combined effect of the high surface area and high conductivity of graphene and π-π stacking interaction between graphene and p-L-Trp.