A disposable, low cost, commercial available electrode, Pencil graphite electrode (PGE), was modified with pyrocatechol violet (Pcv) for electrocatalytic oxidation of hydrazine. To prepare modified electrode, pencil leads were immersed into 0.01 M Pcv solution for 10 min at room temperature. Cyclic voltammetric experiments show that a broadened and highly irreversible peak attributed to oxidation of N₂H₄ was observed at 600 mV at the bare PGE, while a well-defined irreversible oxidation peak was observed at 100 mV at the Pcv/PGE. A shift in the overpotential to more negative direction (about 500 mV) and an enhancement in the peak current indicate that the Pcv/PGE presents an efficient electrocatalytic activity toward oxidation of hydrazine. Then, flow injection analysis (FIA) of N₂H₄ was performed based on its electrocatalytic oxidation at the Pcv/PGE. The recorded amperometric current-time curves in FIA under optimized conditions showed a linear dependence on the N₂H₄ concentration between 2.5 × 10⁻⁴ mM and 0.50 mM with a detection limit of 0.08 μM. This proposed modified electrode exhibits a simple, disposable, low cost, rapid and sensitive determination of hydrazine.