Leaf chlorophyll concentration, chloroplast ultrastructure, Ni concentration in leaves and Ni accumulation in chloroplasts were examined in cabbage plants treated with Ni as organic complexes, i.e. Ni(II)–Glu, Ni(II)–citrate and Ni(II)–EDTA, in the concentrations of 40 and 85 μM. The plants were grown on half-strength Hoagland's nutrient solution at pH 5.3 for a period of 21 days. The Ni(II) complexes have different effects on leaf chlorophyll concentration and degree and specificity of ultrastructural changes of chloroplasts. After Ni(II)–Glu and Ni(II)–citrate treatment at both concentrations of Ni, the leaf chlorophyll concentration was reduced. After Ni(II)–EDTA treatment, it was reduced only at the concentration of 85 μM Ni. After Ni(II)–Glu and Ni(II)–citrate treatment, the electron density of chloroplast stroma and the number of grana were reduced. Accumulation of starch was observed only in those chloroplasts that were located close to vascular bundles. After Ni(II)–Glu treatment, the thylakoids were swollen, but after Ni(II)–citrate treatment, the thylakoids were condensed. After Ni(II)–EDTA treatment, an accumulation of starch and an increase of the number of plastoglobuli were observed. Damage of the thylakoids was observed sporadically. The experiment also showed that there is a relationship between the degree of toxicity of the examined Ni complexes and Ni concentration in leaves. As far as toxicity and Ni bioaccumulation is concerned, the Ni complexes can be put in the following order: Ni(II)–Glu≥Ni(II)–citrate≫Ni(II)–EDTA. The tissue localization of Ni by the silver sulphide method showed differences in Ni accumulation in the chloroplasts. After Ni(II)–Glu and Ni(II)–citrate treatment, Ni accumulation in chloroplasts was higher than after Ni(II)–EDTA treatment.