Peatlands are an important component of the natural landscape of Anticosti Island (Québec, Canada), covering approximately one quarter of its land area. These unique wetlands provide several ecosystem services and play a fundamental role in the natural mitigation of climate change through atmospheric carbon sequestration. The maritime peatlands of Anticosti Island stand out because of their exceptional biodiversity and their unique paleoenvironmental archives of climate variations in the Gulf of St. Lawrence region over recent millennia. The reconstruction of the development of 2 peatlands (Perrier et al., 2022) shows that the ecohydrological conditions and the carbon dynamics were sensitive to past climate variations. More than 12,000 tons of carbon have accumulated under the 2 ombrotrophic domes. In addition, new observations allow us to make the hypothesis of the presence of relic permafrost, most probably formed during the cold period of the Little Ice Age (between 1350 and 1850). This contribution presents a summary of the exceptional natural heritage of the peatlands of Anticosti Island and supports the promotion of their conservation.