Using ZnO nanonails, a hydrazine electrochemical sensor has been fabricated, for the first time, which showed a high and reproducible sensitivity of 8.56 µA cm^–2 µM^–1 with a response time less than 5 s, a linear range from 0.1 to 1.2 µM and a correlation coefficient of R = 0.999. The limit of detection (LOD), based on the S/N ratio, was estimated to be 0.2 µM.