Microplastic pollution is an emerging environmental concern, and polyethylene terephthalate (PET) particles are among the most widespread synthetic polymers. Recent studies suggest that microplastics can act as carriers for biomolecules, including allergens, potentially influencing their transport, persistence, and biological activity. In this work, we investigate the adsorption mechanism of Cry j 1, a major Japanese cedar pollen allergen, onto a PET microplastic surface using atomistic molecular dynamics (MDs) simulations. A PET slab was constructed from a 6-mer repeat unit with CHARMM36 force field parameters and solvated in a TIP3P water box containing physiological ion concentrations. The Cry j 1 structure, obtained from AlphaFold2, was preprocessed and positioned 2 nm above the PET surface using Packmol. Simulations were conducted in GROMACS at 310 K under NPT conditions to monitor protein conformational changes, adsorption energy, hydrogen bonding, and hydrophobic interactions. Preliminary 20 ns trajectories reveal a progressive reduction in protein–surface separation distance, accompanied by stable hydrophobic contacts between PET aromatic rings and Cry j 1 surface residues. Ongoing analyses aim to quantify residue-specific interactions, solvent-accessible surface area changes, and adsorption free energy to better understand the driving forces behind allergen binding. This study provides atomistic insight into allergen–microplastic interactions, offering a predictive framework for assessing environmental exposure risks and informing strategies to mitigate the impact of microplastic-associated allergens in polluted ecosystems.