A new, simple, rapid, sensitive and environmentally friendly ultrasound-assisted emulsification dispersive liquid–liquid microextraction (UAE-DLLME) has been developed for trace nickel Ni(II) separation and preconcentration in environmental samples prior to spectrophotometric determination. The proposed method based on using non-ionic water-soluble surfactant Triton X-114 (TX-114) as a disperser solvent and tetrachloroethylene as an extractive solvent. A 6-(1,3-thiazolylazo)-2-nitrophenol (TANP) as complexing agent was used for complexation of Ni(II) at pH 7.0. The influence of various variables on the performance of the UAE-DLLME method was optimized. Under the optimal conditions, the calibration graph was linear in the rage of 1.0-300 μg L-1. The detection and quantitation limits of the method were determined as 0.3 and 1.0 μg L-1, respectively. The preconcentration factor and enhancement factor were obtained as 60 and 45. Relative standard deviation (RSD %) as precision at 100 and 200 µg L-1 of Ni(II) were 1.4 and 2.1%, respectively (n=10). The validation of the developed method was proved by analysis of certified reference materials. Finally, the developed UAE-DLLME microextraction method was applied to preconcentrate and determine of trace levels of Ni(II) in real water, food and tobacco samples with satisfactory results.