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 collection includes one dataset from each deployment profile (in netCDF format), one tab-delimited file containing isotopic composition of discrete water samples, and the raw 20 Hz measurements of an eddy-covariance station at one of the deployment sites.