Warming can release carbon from organic matter (OM) initially freeze-locked in circumarctic permafrost. The extent of this carbon release depends on OM reactivity. Our understanding of how OM reactivity varies across different terrestrial permafrost types and how it changes during transport from land to marine shelves remains limited. In this study, we measured bulk organic, isotopic and thermogravimetric properties as proxies of OM reactivity on various materials, including bulk deposits and water-soluble fractions (leachates) from terrestrial Holocene and Pleistocene permafrost, bulk surface sediments from the Laptev Sea, and sediment cores from the western Laptev Sea. Bulk OM from terrestrial Pleistocene permafrost exhibited lower reactivity compared to Holocene permafrost. Leachates from terrestrial Pleistocene permafrost displayed slightly higher OM reactivity and younger radiocarbon ages than their corresponding bulk fractions but these values remained lower than those of Holocene permafrost. On the eastern Laptev Sea shelf, a higher contribution of Pleistocene permafrost-derived OM resulted in relatively old radiocarbon ages and reduced OM reactivity in surface sediments compared to the central and western Laptev Sea shelf. A cross-shelf gradient in OM reactivity was observed in the central and western Laptev Sea, with a rapid decrease near the coast followed by a more gradual decline offshore. Downcore analyses revealed that this reduction in OM reactivity reflects primarily degradation during cross-shelf transport rather than after burial. Our results advance the understanding of OM reactivity differences between Pleistocene and Holocene permafrost, as well as changes in terrestrial permafrost OM reactivity during transport and after burial.