Microplastics (MP) are recognised as emerging anthropogenic contaminants and have been observed in biota including commercial produced bivalve species, however only a few studies assess the efficacy of MP depuration in species from aquaculture production. This preliminary study assessed MP depuration efficacy in Pacific oysters (Magallana gigas, n=50) and European flat oysters (Ostrea edulis, n=50). Four depuration times (24, 48, 72 and 96-h) were considered, with 10 individuals per treatment, and an additional 10 control organisms. Organic tissues were digested using a 10% KOH solution (40 ᵒC for 24-hours). Digested tissue was filtered to be subsequently observed for MP isolation. A subsample (109/539) was used for FTIR polymer identification. A forensic approach to cross-contamination was applied to minimise potential sources. Environmental MP concentrations in edible tissue of M. gigas were 0.6 MP g-1 and 0.4 MP g-1 for O. edulis. These were significantly reduced after a 96-hour depuration for both species: 0.2 MP g -1 for M. gigas and 0.1 MP g-1 for O. edulis, respectively. No statistically significant correlation between MP concentration and weight of edible tissue of oysters were identified. MP isolation retrieved mainly fibres and polymer identification revealed that 51.6% of these were natural. Main outputs of this research showed that increasing depuration time to 96-hour can significantly reduce MP concentrations in edible tissues of farmed oysters. These findings aligned with similar depuration studies that show reduction; however, this is the first trial to demonstrate a significant decrease in MP concentrations over 96-h. These results provide important industry advice and can contribute to policy design, by providing valuable baseline information to stakeholders on MP reduction in bivalves intended for human consumption.