Nitrous oxide (N2O) is a potent greenhouse gas that is naturally produced as a byproduct of nitrogen cycling. Eutrophication elevates nitrogen availability and enhances low-oxygen conditions, thus altering nitrogen cycling and associated N2O availability, but a knowledge gap persists regarding controls on N2O across estuarine environments. I studied three adjacent and nutrient-rich tidal tributaries of the Patapsco River (MD), one of which has engineered aeration (Rock Creek), to quantify how aeration and alterations to oxygen availability and nitrogen cycling will impact N2O production. In all creeks, N2O concentrations were above atmospheric levels and served as a source of N2O to the atmosphere. Oxygen and nitrate availability were most associated with variations in N2O concentrations, and N2O concentrations and air-water fluxes were highest in Rock Creek, especially during summer under non-aerated, but moderately oxygenated conditions. These new data help broaden our understanding of N2O cycling, availability, and distribution within estuarine ecosystems.