<p>Nanoparticles in agroecosystems and natural environments has raised concerns, but nanoparticle uptake and toxicity in soil, plants, and animals is not yet understood. Unlike other studies that evaluated nanomaterials under laboratory conditions, this research aimed to evaluate increasing concentrations of Fe NPs (magnetite [Fe₃O₄] and hematite [α-Fe₂O₃]) on fern plants (<i>Pleopeltis guttata</i> [Maxon]) and endogenous earthworms (<i>Balanteodrilus sp</i>.) in a controlled space of a pine-oak forest. The results revealed that in possible contamination by Fe NPs, nanometric iron remains up to 90 days after application, which enables plants and earthworms to absorb nanometric Fe from the soil. The bioconcentration results revealed that <i>P. guttata</i> ferns are not plants capable of accumulating nanometric iron. On the contrary, the ferns limit the bioaccumulation of iron in the leaves and stems. When determining the translocation factor, it turned out that the plants immobilized the iron in the roots. In addition, the iron accumulated in the roots decreased with increasing concentrations of NPs. On the other hand, the study revealed that earthworms consume nanometric iron from the soil and that the amount of accumulated iron is a function of increasing concentrations. Although this study is the first to evaluate the effects of Fe NPs on ferns and earthworms simultaneously, future research should include an assessment of biochemical parameters and mineral concentrations in these organisms.</p>