In recent times, there has been a significant rise in global arsenic intake, stemming from both drinking water and food sources. Arsenic contamination in groundwater can originate from natural geological processes and anthropogenic activities such as industrial effluents, agricultural practices like insecticide use, municipal sewage, and household waste. One eco-friendly and dependable method for addressing this issue involves the synthesis of metal complex nanoparticles, which have broad applications in various fields, including sensing, catalysis, and environmental remediation. A noteworthy development is the creation of a novel Nano Hydrazinyl Schiff Base Co(II) Complex sensor designed specifically for detecting arsenic with high sensitivity and selectivity. This Nano Hydrazinyl Schiff Base Co(II) Complex underwent comprehensive characterization using a range of analytical tools, including Dynamic Light Scattering (DLS), Zeta potential analysis, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FT-IR), contact angle measurements, as well as BET surface area and pore size determination. The nanoparticles exhibited excellent water dispersibility, high surface area, and favorable hydrophobic properties, making them suitable for sensing applications in aqueous environments. Furthermore, researchers explored the practical application of the Nano Hydrazinyl Schiff Base Co(II) Complex as a simple, cost-effective, and highly sensitive Quartz Crystal Microbalance (QCM) sensor for rapidly detecting arsenic. Using this Nano Hydrazinyl Schiff Base Co(II) Complex sensor, arsenic can be reliably detected even at deficient concentrations, as low as 1 ppm, with a remarkable response time of 7-8 minutes. Additionally, the cytotoxicity of the Hydrazinyl Schiff Base Co(II) Complex nanoparticles was thoroughly investigated to ensure their safety. This innovative method has demonstrated its effectiveness and feasibility for precisely determining arsenic ions in groundwater and industrial effluent wastewater samples.