Herein, we report the fabrication and characterization of phenyl hydrazine sensor based on ytterbium (Yb) doped ZnO flowers composed of nanorods prepared by simple hydrothermal process. The as-synthesized nanomaterial was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) attached with energy dispersive spectroscopy (EDS), Fourier transformation infrared (FTIR) and Raman-scattering spectroscopy which revealed the large-quantity synthesis, well-crystallinity and wurtzite hexagonal crystal structure of Yb-doped ZnO flowers. The fabricated phenyl hydrazine chemical sensor, by employing Yb-doped ZnO flowers as an electron mediator, exhibited sensitivity of ∼34.2 µA·mM-1 ·cm-2, detection limit of 24 mM and linear dynamic range of 0.25-4.0 mM. The presented work demonstrates that the Yb-doped ZnO nanomaterials are promising electron mediator which can be used for the fabrication of chemical sensors to detect various hazardous and toxic chemicals as phenyl hydrazine.