A voltammetric sensor was developed using a nitrogen-doped porous carbon and nitrogen-doped graphene nanocomposite modified glassy carbon electrode for the simultaneous determination of dopamine (DA), uric acid (UA) and ascorbic acid (AA). Detailed characteristics of the nanocomposites were investigated by SEM, TEM, XPS, XRD and FT-IR. Experimental conditions such as accumulation time, accumulation potential and buffer solution pH were optimized. The sensor demonstrated a linear plot of 0.01–15.0 mmol L⁻¹ for AA, 0.08–350.0 μmol L⁻¹ for DA, and 0.5–100.0 μmol L⁻¹ for UA, with detection limits of 1.99 μmol L⁻¹, 0.011 μmol L⁻¹ and 0.088 μmol L⁻¹, respectively. The established method exhibited excellent reproducibility, anti-interference and stability, and it was applied to DA, UA and AA determination in real urine samples with recoveries between 100.2% and 102.0%.