A pyrolytic method is described for preparation of ultrafine FeC nanoparticles incorporated into N-doped graphitic carbon nanosheets (FeC@NGCSs). Iron phthalocyanine and graphitic carbon nitride (g-CN) are used as starting materials. The hybrid nanocomposite was placed on a glassy carbon electrode (GCE) and then applied to simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and xanthine (XA). Figures of merits are as follows: for AA, the linear response range covers the 54.0-5491.0 μM range, the lower detection limit is 16.7 μM, and the best working voltage (vs. the saturated calomel electrode (SCE)) is 0.05 V. The respective data for DA are 1.2-120.8 μM, 0.34 μM and 0.19 V (vs. SCE). For UA, the respective data are 4.8-263.0 μM, 1.4 μM and 0.32 V (vs. SCE), and for XA the data are 4.8-361.0 μM, 1.5 μM and 0.71 V (vs. SCE). The method was successfully applied to their simultaneous determination in spiked serum samples. Graphical abstract Ultrafine FeC nanoparticles embedded in N-doped graphitic carbon sheets for simultaneous determination of ascorbic acid, dopamine, uric acid and xanthine.