The determination of trace metals is very crucial in order to identify their functionalities in the human body and help to protect human health. For this purpose, a sensitive and accurate analytical method was developed to determine nickel at trace levels by flame atomic absorption spectrometry after preconcentration with switchable solvent based liquid phase microextraction. Experimental conditions of the method were systematically optimized to maximize the extraction yield. Nickel was complexed with a Schiff base ligand synthesized from the reaction of 1- naphthylamine and 5-bromosalicylaldehyde to obtain an insoluble and easy to extract compound. Under the optimal conditions of the developed system, analytical figures of merit were determined. The relative standard deviation for the lowest concentration in the dynamic working range was under 11% which demonstrated good precision. The enhancement in detection power recorded by the switchable solvent based liquid phase microextraction-flame atomic absorption spectrophotometry compared the conventional flame atomic absorption on the basis of detection limit was approximately 40-fold. The applicability and accuracy of the developed method were investigated by spiking tap water with nickel and the recoveries were from 91 to 98%.