In this study, we report the amperometric and impedimetric determination of hydrazine at a novel trimethine cyanine dye, 1H-Benz[e]indolium, 2–[3–(3–butyl–1, 3–dihydro–1, 1–dimethyl–2H-benz[e]indol–2–ylidene)–1–propenyl]–1, 1, 3–trimethyl–, hexafluorophosphate (DVD-R dye A4) or (DVDR) film modified glassy carbon electrode (GCE). The DVDR film was electrochemically deposited on a GCE surface by performing 20 consecutive cyclic voltammograms at the scan rate of 100 mV s-1in the potential range between -0.8 and 2.0 V in 0.1 mM DVDR in 0.1 M H2SO4 solution. The SEM and AFM results revealed that DVDR film surface possess both flake and bead like structures. Cyclic voltammetry (CV) results demonstrated that DVDR film was electrochemically active and it showed a pair of well-defined redox peaks at a formal potential (E°′) of 5.5 mV in pH 7. Electrochemical impedance spectroscopy (EIS) results showed that rapid electron transfer process occurs at the DVDR/GCE surface than the bare/GCE surface. The electron transfer resistance (Ret) values obtained at the DVDR film increased linearly with increase in hydrazine concentrations between 0.05 mM–1.07 mM, which confirmed the excellent impedimetric hydrazine quantification. The DVDR film showed rapid amperometric i-t response towards hydrazine in the linear concentration range between 1 x 10–6 M–2.22 x 10–4 M with a sensitivity of 0.571 μA μM-1 cm-2 of hydrazine. Even though large amounts (1000/500–fold) of the common cations/anions coexist in the same supporting electrolyte, they do not produce any notable interference effect with the hydrazine oxidation signal, which validates the high selectivity of DVDR film for hydrazine. Moreover, acceptable recovery was achieved at the DVDR/GCE in hydrazine spiked various water samples, which confirmed the practical applicability of the developed sensor.