The aim of the study was to investigate the effect of the Fe3O4 nanoparticles (Fe-NPs) on the germination of sunflower seeds, early growth of seedlings and the concentration of selected elements in seedlings. The influence of constant magnetic fields in systems with and without Fe-NPs was investigated. Experiments were done on seeds subjected to germination under constant magnetic field (0 (control), 5, 25 and 120 mT) for 7 days in the presence of solution containing 0, 50 or 500 ppm Fe-NPs. No significant effect of Fe-NPs and the magnetic field on germination of seeds and the growth of seedlings has been demonstrated. In most cases, a decrease in germination parameters was observed. For the majority of samples the relative decrease in the concentrations of elements was demonstrated mainly for samples without Fe-NPs. Interestingly, a significant decrease in the concentrations of trivalent (including iron - Fe) and toxic elements in samples containing Fe-NPs in relation to control samples was observed. The authors suggest that in this case the binding (adsorption) of these elements in the roots and seeds of the sunflower by Fe-NPs took place. This explains the lower iron content in seedlings than in seeds prior to sowing.