Among the abiotic stress of serpentine soil for plants, high nickel (Ni) concentration in soil caused toxicity to plants, and restricts plant species inhabiting on the serpentine soil. This phenomenon has suggested its relationship with iron (Fe) deficiency. Excess Ni complexes with ligand materials such as nicotianamine and citrate, resulting competitively inhibition of chelate formation and transport system of Fe(II) in plants. However, Ni uptake mechanism into plants and its competition with Fe transport was not cleared. We made a hypothesis that Ni was transported into plant roots through Fe uptake system, and demonstrated using hydroponically cultivated Arabidopsis thaliana. Excess Ni exposure increased Fe accumulation, and Fe-deficient treatment increased Ni accumulation in roots. Excess Ni exposure increased relative transcription level of AtIRT1, the primary Fe(II) uptake transporter, and also FRO2, a ferric reductase in the root epidermis, and FIT, a transcription factor regulating the expression of genes involved in Fe homeostasis. Our findings suggest that excess Ni causes Fe deficiency at the molecular level and induces Fe deficiency signaling in plant cells. Our field research of plants inhabiting on serpentine soils of Sugashima Island, Japan, resulted in the highest correlation between Fe and Ni contents in these plants, among the relationship between other metals. This result also suggested that active Fe uptake could be a counterplot of Ni toxicity, and one of the key characteristics for plant adaptation to and survival on the serpentine soils.