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 the stable water isotopic composition of precipitation, snowpack, and fjord water collected in Svalbard and coastal Norway during the ISLAS2020 measurement campaign. We collected precipitation samples at Ny-Ålesund, Longyearbyen, Tromsø, Andenes, Ålesund, and Bergen, on a daily or twice-daily basis. More frequent sampling was conducted across two intense observational periods from 29 February to 3 March and from 12 to 15 March. Surface snow, hoar frost, and fjord water samples were also collected in Ny-Ålesund, to characterize the surfaces with which atmospheric vapor could interact/exchange during profiling efforts. Additionally, we collected snowpack samples up at Zeppelin observatory, as well as snow pit samples from Gruvebadet. Analysis of collected samples was performed at FARLAB, University of Bergen, in Bergen, Norway, via cavity ring-down spectrometers. The collections span 34.67 days, from 2020-02-20 2:00 to 2020-03-25 18:00 UTC.