This dataset includes nitrate isotopes and relevant hydrographic and chemical parameters (temperature, salinity, nitrate, phosphate, dissolved oxygen, and so on) observed in the South China Sea basin and the adjoining western North Pacific Ocean during 2011 and 2014. Nitrate isotopes were measured by the denitrifier method. Nutrients were analyzed onboard using a Technicon AA3 Auto-Analyzer (Ban-Lube, GmbH). Dissolved oxygen (DO) was determined using the Winkler method. These data were used to elucidate nitrate dynamics in these regions.