An efficient, quick, sensitive, and eco-friendly ultrasound-assisted emulsification dispersive liquid-liquid microextraction (UAE-DLLME) method was developed for the separation and preconcentration of trace nickel (Ni(II)) in environmental samples before spectrophotometric analysis. The non-ionic water-soluble surfactant Triton X-114 (TX-114) was used as a dispersive solvent, while tetrachloroethylene served as the extractive solvent, rendering the microextraction method more environmentally friendly. The novel complexing agent, 4-((2, 4-Dihydroxyphenyl)diazenyl)-N-(pyrimidin-2-yl)benzene sulfonamide (DHPDPNS), was employed for the complexation of Ni(II) at a pH of 7.0. The impact of multiple variables on the efficacy of the UAE-DLLME approach was optimized. Under ideal conditions, the calibration graph exhibited linearity within the range of 2.0-500 μg L-1. The detection and quantification limits were established at 0.6 μg L-1 and 2.0 μg L-1, respectively. The preconcentration factor and enhancement factor were determined to be 60 and 30, respectively. The relative standard deviation (%RSD) indicating precisions at 200 and 400 μg L-1 of Ni(II) was 1.7% and 2.0%, respectively (n=10). The developed UAE-DLLME microextraction method was ultimately employed to preconcentrate and quantify trace quantities of Ni(II) in environmental samples