During a 5-week measurement campaign (ISLAS2020) in February and March 2020, we collected measurements of the stable isotope composition in atmospheric water in Svalbard and along the Norwegian coast. This included discrete collecting of precipitation at Ny-Ålesund, Longyearbyen, Tromsø, Andenes, Ålesund, and Bergen. Additionally, Ny-Ålesund hosted the primary field experiment of the campaign, with a cavity ring-down spectrometer (CRDS) installation, measuring the in-situ stable isotope composition of the ambient air at three deployment sites. At two of these sites, we performed near-surface vertical profiling of stable water isotopes, to quantify the isotopic gradients above the snow-covered tundra and the open fjord water. These profiles were collocated with high-resolution temperature measurements from fiber-optic distributed sensing methods. At each of the three CRDS deployment sites, automated weather stations logged the ambient meteorological conditions. In addition to the precipitation collected at Ny- Ålesund, we took multiple samples of local snowpack and fjord water (Kongsfjorden). All stable water isotope measurements have been calibrated onto the VSMOW-SLAP scale. Vapor measurements from Ny- Ålesund have also been corrected for mixing ratio - isotope ratio dependency. The data from the ISLAS2020 measurement campaign can facilitate studies on phase changes in the atmospheric water cycle using stable water isotopes as a constraint.This dataset contains observational data from the Zeppelin deployment site at Ny-Ålesund, Svalbard, Norway, during the ISLAS2020 field experiment. The primary purpose for the collection of this dataset was to obtain free-tropospheric, in-situ stable water isotope measurements in atmospheric water vapor. These measurements were obtained with a cavity ring-down spectrometer installed at the Zeppelin mountain observatory. During this deployment, the instrument was connected to various inlets, across three subdeployment periods. The ambient meteorological conditions associated with these isotopic measurements are provided by an automated weather station. The observational period lasts 65.0 hours (about 2 and a half days), from 2020-02-29 15:30:00 to 2020-03-03 08:30:00 UTC.