This study assessed the effects of nanoplastics (NPs) using for the very first time microfluidic devices (chip) mimicking transition waters. Three kinds of NPs were tested: crushed NPs from polystyrene pellets (NP-PS), or from Guadeloupe beaches (NP-G); and latex PS (PSL-COOH). The eluted fractions from the microfluidic device showed a low aggregation of NPs. They remained stable over time in the exposure media, with a stabilization of NPs of small sizes (< 500 nm). These chips were thus used for the toxicological assessment of NPs on swamp oysters, Isognomon alatus. Oysters were exposed for 7 days to the chip elution fraction of either NP-G, NP-PS or PSL-COOH (0.34–333 µg.L−1). Gene transcription analyses showed that the tested NPs triggered responses on genes involved in endocytosis, mitochondrial metabolism disruption, oxidative stress, DNA repair, and detoxification. Highest responses were observed after NP-G exposure at low concentrations (1 µg.L−1), as they are originated from the natural environment and accumulated contaminants, enhancing toxicological effects. As salinity influences aggregation and then the bioavailability of NPs, our results demonstrated the importance of using microfluidic devices for ecotoxicological studies on swamp or estuarine species.< Leer menos