Non-enzymatic electrochemical sensor for organophosphate pesticide (Parathion) has been developed for the first time by utilizing nickel oxide nanoplatelets modified screen-printed electrodes (SPEs). The NiO NPLs showed a superior electrochemical performance and ultrasensitive determination of parathion in real samples over bare/unmodified SPEs. Display omitted •Meso-/macro-porous NiO nanoplatelets were synthesized by a simple hydrothermal method.•Sensitive determination of parathion pesticide by utilizing NiO NPLs modified SPE was explored.•NiO-SPEs can be used in a wide concentration range with low detection limit of 24 × 10−9 mol L−1.•The stability of NiO-SPEs nanozyme was utilized for detection of parathion in water, urine and vegetable samples. Nanozyme-based electrochemical sensors have attracted much attention because of their low cost, sensitivity and remarkable stability under extensive environmental and industrial conditions. Interestingly, the physical characteristics of the nanomaterials in terms of size, shape, composition, surface area and porosity dominate the electrochemical processes at electrode surfaces. Herein, we explore nickel oxide nanoplatelets (NPs) modified screen-printed electrode-based nanozyme sensors that displays high electrochemical activity including stability, sensitivity, selectivity and applicability for organophosphate pesticide (Parathion) determination. Differential pulse voltammogram of NiO-SPE in presence of parathion showed a characteristic peak current at −1.0 V (vs. Ag/AgCl). The NiO-SPE platform allows determination of parathion over the concentration range of 0.1–30 µM with a limit of detection (LOD) of 0.024 µM. The sensing platform is found to detect parathion of interferences without compromising the sensitivity of the sensor. Such interesting features offer a sensitive determination of parathion in water, urine and vegetable samples.