Our study contributes to the development of sustainable technologies for wastewater treatment by evaluating the toxic effects of bare magnetite nanoparticles and functionalized with the enzyme laccase at different stages of the zebrafish life cycle. We found no negative impact on embryo hatching, survival rates, or larval behavior. Additionally, we evaluated the accumulation of nanoparticles in various stages of zebrafish. We found that, although there was accumulation during embryonic stages, it did not affect normal development or subsequent hatching. Iron levels in different organs such as gills, muscles, gastrointestinal tract, and brain were also evaluated in adults. Although iron levels may increase depending on the dose and exposure method applied, they were not statistically significant with respect to the control groups. Our findings suggest that bionanocomposites evaluated here can be used safely for the removal of contaminants in wastewater without toxic effects or detrimental accumulation to the health of the animal.