The release of legacy fallout radionuclides (FRNs) in response to glacier retreat is a process that has received relatively little attention to date, yet may have important consequences as a source of secondary contamination as glaciers melt and down-waste in response to a warming climate. The prevalence of FRNs in glacier-fed catchments is poorly understood in comparison to other contaminants, yet there is now emerging evidence from multiple regions of the global cryosphere for substantially augmented FRN activities in cryoconite. These data describe activities of FRNs in both cryoconite and proglacial sediments collected from the Isfallsglaciären catchment in Arctic Sweden in 2017 based on gamma spectrometry. The data presented here also includes particle size analysis for all samples, and both Wavelength-dispersive X-Ray fluorescence spectrometry and stable isotope analysis data for cryoconite samples, providing insight to major and minor elements and organic content.