Submitted: 17 February 2025 You are already at the latest version The present study investigated the gut contents of oysters cultivated in the Emboraí Velho Estuary (Amazonian littoral) focusing on the analysis of diatoms. Analyses of the stomach contents from 60 adult individuals of the species Crassostrea gasar (Adanson, 1757) collected in the study environment were performed. Additional water samples were collected for the analysis of diatoms present in the estuary.