In the present study, facile and competent homogeneous liquid–liquid microextraction via flotation assistance (HLLME-FA) method combined with flow injection flame atomic absorption spectrometry (FI-FAAS) was proposed for simultaneous separation/preconcentration and determination of trace amounts of cadmium and copper in water samples. The efficient 2-(3,4-dihydroxyphenyl)-1,3-dithiolane (DHPDTO) with thiol groups was used as chelating reagent. The predominant parameters influencing the HLLME-FA, such as solution pH, concentration of DHPDTO, extraction and homogeneous solvent types and volumes, ionic strength, and extraction time were studied. Applying all the optimum conditions in the process, the detection limits of 0.008 and 0.01 μg L−1, linear ranges of 0.08–40 and 0.1–45 μg L−1, and the precision (RSD%, n = 7) of 3.4 and 3.9 % were obtained, respectively, for cadmium and copper. The proposed procedure showed satisfactory results for analysis of tap water, river water, well water, and seawater.