In the present study, the simple and efficient method of ligandless-ultrasound-assisted emulsification-microextraction (LL-USAEME) has been developed for the simultaneous preconcentration and determination of chromium and zinc in water samples by inductively coupled plasma-optical emission spectrometry (ICP-OES). Tetrachloroethylene was selected as the extraction solvent. A fractional factorial design (2⁵⁻¹) and a Box–Behnken design (BBD) were used to identify and optimize the most important parameters that influence the ultrasound microextraction process. The optimum levels of the effective parameters were: 190 μL for volume of extraction solvent, 11.4 for pH, 15% (w/v) for the salt concentration and 5 min for sonication time. Under the optimum conditions, the relative standard deviations (RSDs, C = 100 μg L⁻¹, n = 7) were 2.5% and 3.1% for Cr and Zn respectively. The calibration graphs were linear in the range of 0.5–1500 μg L⁻¹ for both the metal ions with determination coefficients (R²) of 0.997. The limits of detection (LODs) for Cr and Zn were 0.20 and 0.28 μg L⁻¹, respectively. The proposed method was successfully applied to the analysis of three real environmental water samples and satisfactory recoveries (90–109%) were achieved.