A comprehensive risk assessment of plastics’ health impacts is imperative; however, significant gaps exist in toxicity models that closely simulate human ingestion. The biotransformation of micro−/nanoplastics (MNPLs) during the digestion process, along with their bioaccessibility, can significantly influence their toxicity. This chapter presents a simplified in vitro digestion protocol tailored for cytotoxicity assessment, providing a more realistic simulation of MNPLs ingestion. By enhancing the physiological relevance of laboratory models, this approach offers a valuable tool for improving the accuracy of human health risk evaluations related to plastic exposure.