Lithium adsorption on the surface of magnetite, lepidocrocite, and maghemite particles was studied at different pH values in LiOH and Li2CO3 solutions under redox conditions and temperatures relevant to the water chemistry of CANadian Deuterium Uranium (CANDU) reactors. Lithium adsorption on maghemite shows a different behavior than on lepidocrocite and magnetite. It is concluded that specific adsorption is the dominant adsorption mechanism on maghemite while lithium adsorption on lepidocrocite and magnetite is nonspecific. However, lithium intercalation into the spinel structure of magnetite and maghemite is also likely. The introduction of O2 reduces lithium adsorption on magnetite. The adsorption behavior of lithium on iron oxides is important to understand the lithium hideout and return in the heat transport system during shutdown and restart of CANDU reactors.