This study investigates whether nanoplastics are significant contributor of rare earth elements (Gd) transportation under environmental conditions. Important effects of nanoplastic concentration, Gd concentration, complexation with organic ligands, pH, ionic strength and occurrence of natural colloids competitor were studied thanks to an experimental design combining incubation follow by ultrafiltration and ICPMS analyses. In particular, we observed that even in sea water, about half of the gadolinium can be adsorbed on nanoplastics. Surprisingly, the adsorption is more pronounced at low concentration of nanoplastic (10 μg L−1) probably because it prevents homoaggregation of nanoparticles. These are the first experimental clues that adsorption on nanoplastics is governed by fundamentally different processes than adsorption on microplastics.