The Arctic stores vast amounts of carbon across interconnected terrestrial and marine reservoirs and has acted as a sink of anthropogenic carbon to date. However, steadily increasing atmospheric greenhouse gas concentrations and rapid Arctic warming, currently three to four times faster than the global average, are intensifying carbon cycling across the region. While sea-ice retreat exposes larger ocean surfaces to atmospheric carbon dioxide (CO₂) uptake, emissions of CO₂ and methane (CH₄) from thawing permafrost, inland waters, and disturbance-affected ecosystems are rising. Current scientific discourse increasingly focuses on whether the Arctic terrestrial biosphere is shifting from a net sink to a net source of CO₂ and whether its CH₄ emissions are rising. Despite major advances and synthesis efforts, substantial uncertainties remain in quantifying Arctic carbon fluxes due to sparse observations, spatial heterogeneity, and inconsistencies between bottom-up and top-down approaches. These knowledge gaps limit our ability to quantify Arctic carbon–climate feedbacks and to assess their implications for the global carbon budget and international climate policy. To address these challenges, an international, interdisciplinary workshop on the Arctic Carbon Cycle was held in Berlin, Germany, in September 2025. The meeting gathered ~40 participants from terrestrial and marine Arctic carbon research, policy, and the science–policy interface. Through keynote presentations, panel discussions, and open exchanges, participants assessed current understanding of the coupled Arctic carbon system, identified key knowledge gaps and research priorities, and explored pathways to strengthen interdisciplinary collaboration and policy dialogue.