A new synergetic salt- and acid-induced ligandless mixed micelle cloud point extraction procedure was developed for the simultaneous separation and preconcentration of Cd, Hg, Bi, and Tl from petrochemical effluents and groundwater samples. The cationic mixed micelles are formed by the micelle-micelle interaction of cationic cetylpyridinium ammonium bromide (CPAB) and nonionic Triton? X-114 micelles, which act as an ion pair and extracting agent. Due to the synergetic effect of potassium iodide and sulfuric acid, the hydrophilic anionic Cd, Hg, Bi, and Tl iodide species are formed. These also induce the clouding phenomenon in cationic mixed micelles. The strong electrostatic interaction between the mixed micelles head groups and the anionic iodide species form the hydrophobic ion pairs which are separated from the bulk aqueous phase into a small mixed micelle-rich phase, thus avoiding the addition of an external chelating agent. Under the optimized conditions, a pre-concentration factor of nearly 20 times was obtained for all of the elements. The limits of detection obtained were 0.0005, 0.2, 0.04, and 0.05 ng mL-1 for Cd, Hg, Bi, and Tl, respectively. The recoveries were in the range of 93–102% at 0.1 to 10 ng mL-1 with a relative standard deviation of 2–10%. The accuracy of the method was validated by analysis of certified reference materials BCR 714 Initial Influent, BCR 715 Industrial Effluent, BCR 610 Groundwater, and NIST 1643e, 1643f, and 1642b Trace Elements in Water. The method was also applied to real samples of petrochemical effluents and groundwater collected locally. A continuum source electrothermal atomic absorption spectrometer (CS-ETAAS) was used for the determination of the elements.