Peat properties data and age depth models for 102 peat cores extracted and analysed for the Increased Carbon Accumulation in Arctic Peatlands (ICAAP) project (Grant NE/S001166/1). Peat cores were extracted from 12 peatland sites from four regions of the Arctic: Svalbard (78.09065°N 14.98407°E; 78.98595°N, 11.98246°E; and 78.95872°N, 11.68331°E), Norwegian and Finnish Lapland (70.11876°N, 28.48351°E; 69.80659°N, 27.19732°E; and 69.38787°N, 24.24123°E), Nunavut, Canada (72.655515°N, 78.061646°W; 72.694207°N, 77.864603°W; and 73.13028°N, 80.022987°W), and Quebec, Canada (62.165681°N, 75.915017°W; 62.123168°N, 75.769467°W; and 62.157355°N, 75.607301°W). Data originates from the analysis of Arctic peat cores for changes in rates of lateral expansion and vertical peat accumulation during recent centuries. Specifically, peat cores were analysed for moisture content (%), dry bulk density (g cm-3), C/N content (%), 210Pb activity levels (bq/kg), and 14C radiocarbon age (yr BP).