Here, we present a comprehensive isotopic survey of 535 water samples taken in 2018–2019 of the lakes, streams, and other surface waters of the periglacial Pituffik Peninsula in far northwest Greenland. The δ18O, δ2H, and deuterium-excess values of these samples represent 196 unique sites across the peninsula, and we collected the samples to improve our understanding of environmental drivers of water isotopic composition in the High Arctic. Water samples were collected by hand, sealed to prevent evaporation, and shipped to the University of Oulu, Finland, for isotopic analysis. Sampling took place from June through August 2018, in November 2018, and in July 2019. Additional hydrological and geographic data is provided for sampled lakes, including surface area, watershed area, distance from the ocean, and distance from the Greenland ice sheet.