Arctic river deltas and ice-rich permafrost regions are highly dynamic environments which will be strongly affected by future climate change. Rapid thaw of permafrost (thermokarst and thermo-erosion) may cause significant mobilization of organic carbon, which is assumed to be stored in large amounts in Arctic river deltas and ice-rich permafrost. This study presents and compares new data on organic carbon storage in thermokarst landforms and Arctic river delta deposits for the first two meters of soils for five different study areas in Alaska and Siberia. The sites include the Ikpikpuk river delta (North Alaska), Fish Creek river delta (North Alaska), Teshekpuk Lake Special Area (North Alaska), Sobo-Sise Island (Lena river delta, Northeast Siberia), and Bykovsky Peninsula (Northeast Siberia). Samples were taken with a SIPRE auger along transects covering the main geomorphological landscape units in the study regions. Our results show a high variability in soil organic carbon storage among the different study sites. The studied profiles in the Teshekpuk Lake Special Area – dominated by drained thermokarst lake basins – contained significantly more carbon than the other areas. The Teshekpuk Lake Special Area contains 44 ± 9 kg C/m2 (0-100 cm, mean value of profiles ± Std dev) compared to 20 ± 7 kg C/m2 kg for Sobo-Sise Island – a Yedoma dominated island intersected by thaw lake basins and 24 ± 6 kg C/m2 for the deltaic dominated areas (Fish Creek and Ikpikpuk). However, especially for the Ikpikpuk river delta, a significant amount of carbon (25 ± 9 kg C/m2) is stored in the second meter of soil (100-200cm). This study shows the importance of including deltaic and thermokarst-affected landscapes as considerable carbon pools, but indicates that these areas are heterogeneous in terms of organic carbon storage and cannot be generalized. As a next step, the site-level carbon stocks will be upscaled to the landscape level using remote sensing-based land cover classifications to calculate the carbon storage potential for Arctic deltas and larger thermokarst regions, to estimate mobilization potentials from thermokarst and thermo-erosion, and to provide input data for future permafrost carbon feedback models.