Iron(III) colloids are known to act as carriers for toxic elements in nature, which can cause retardation or even acceleration of their migration. In this study the adsorption of UO22+ on iron(III) (oxy)hydroxides (2-line ferrihydrite, 6-line ferrihydrite, goethite, and maghemite) were compared through adsorption isotherm measurements. The normalized adsorption amounts on goethite were larger than those of the other minerals over a wide range of free UO22+ concentration in spite of the relatively small site density of goethite.