This dataset presents the first fully continuous monitoring of water vapour isotopic composition at Neumayer Station III, Antarctica, for two years, from February 2017 to January 2019. In January 2017, a PICARRO L2140-i cavity ring-down spectroscopy analyser was installed in a laboratory room at Neumayer Station. The Picarro analyser runs continuously and measures the injected water vapour content and its isotopic composition approximately every two seconds. For our analyses, the data are reported as hourly mean values.