The present work reports impedance based electrochemical sensing and remediation of 4-nitro phenol (4-NP) using biosynthesized (CuO) copper oxide nanoparticles. The synthesis of CuO nanoparticles is achieved using fruit extract of plant Fortunella japonica as reducing and stabilizing agent. The CuO nanoparticles were characterized using various analytical techniques like UV–Visible spectroscopy, Atomic force microscopy (AFM), High resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray diffraction (XRD). For electrochemical sensing of 4-NP, the CuO nanoparticles were drop casted on screen printed electrode (SPE) and electrode is referred at SPE/CuONPssensor. The mechanism of 4-NP redox reactions was examined using cyclic voltammetry (CV). The electrochemical sensing of 4-NP has been done using square wave voltammetry (SWV) and impedance spectroscopy. In SWV, the oxidation peak current increased with increase in the concentration of 4-NP from 10 nM to 10 mM having regression coefficient of 0.996. In impedometric sensing, change in charge transfer resistance (Rct) with change in 4-NP concentration was used as a signal. The Rctdecreased with increase in 4-NP concentration which is in accordance with SWV results. The effect of solution pH on impedometric response of SPE/CuONPssensor was also evaluated. The SPE/CuONPssensor exhibited good reproducibility and selectivity towards the analyte and is able to perform real sample analysis. The CuO nanoparticles act as a catalyst and showed good degradation percentage of 4-NP pollutant. © 2016 Elsevier B.V.