This paper discusses the potential application of soil washing to Agent Orange/Dioxin-contaminated soil in southern Vietnam through the series of treatability tests. The dioxin content (TEQ) of clean sands ranged from 200 to 3,200 pg/g as compared to the feed soils of 6,600 to 57,000 pg/g. The removal efficiencies of hydrocyclone were between 60% and 85%, and the removal efficiencies were greatly improved to approximately 95%, when flotation technique was employed for further treatment of hydrocyclone underflow (UF). It is estimated that soils contaminated with up to 24, 000 pg/g could be treated to the concentration below any one of the dioxin criteria in Vietnam, that is, commercial/industrial area (1,200 pg/g), green area/park (600 pg/g), and residential area (300 pg/g) using the soil washing system. The recovery rate of clean products (sand and gravel) was expected to be between 65% and 75%. The dioxin concentration rates of the froth (the froth-to-UF rates) in the flotation system ranged at high levels of 17.5 to 78.3 times (an average of 46.4 times), and the froth generation ratios remained at low levels (an average of 2.3%). The above results indicate that the soil washing system with flotation makes it possible to achieve both a high removal efficiency of dioxin and a high volume reduction rate of feed soils, and can be practically used in southern Vietnam for remediation of dioxin contaminated soils.