A green extraction spectrophotometric method was presented for the determination of trace amounts of cadmium in soil and sediment samples. This method is based on the selective extraction of cadmium as its iodide complex by aqueous biphasic extraction composed of polyethylene glycol (PEG) and sodium sulfate, and a subsequent sensitive determination by spectrophotometry using 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol. This extraction method is simple and environmentally benign, since the organic solvents used for the traditional liquid-liquid extractions are replaced by the non-toxic polymer and inorganic salt. Cadmium can be selectively extracted from soil and sediment samples into the PEG-rich upper phase by an aqueous biphasic system containing potassium iodide and sulfuric acid. The proposed method was applied to the determination of cadmium in certified reference materials for soil and river sediment. The obtained results were in good agreement with the certified values.