Two different nitrogen-doped reduced graphene oxides (N-rGOs) were used to modify glassy carbon electrodes (GCE/N-rGOs) as electrochemical sensors for the detection of dopamine (DA). For comparison, GCE/rGO was also studied. The N-rGOs were synthesized via hydrothermal treatment of graphene oxide (GO) with the N-dopants amitrole and urea. The resultant graphene materials exhibited distinct types and distributions of nitrogenated functional groups, but they possessed a similar oxygen content, thus avoiding interference from oxygenated groups. Pyridinic nitrogen was introduced into the rGO structure when amitrole was used as the N-dopant, whereas pyrrolic nitrogen was preferentially formed in the reaction with urea. After optimization of several experimental parameters and sensor calibration, the GCE/pyrrolic-N-rGO electrode was found to exhibit superior electrochemical performance compared with the pyridinic-N-rGO one, demonstrating a limit of detection and sensitivity of 335 nM and 3.51 μA μM−1, respectively. This sensor also showed better selectivity in the presence of interfering agents in the forms of ascorbic and uric acids. A significant improvement of sensor parameters can be explained in terms of the contribution of electrons derived from the pyrrolic structure to the delocalized C sp2-conjugated graphene system.