The Arctic tundra is a significant source of CH4 emissions that are generated through anaerobic methanogenesis, and vegetation has explained much of the heterogeneity in CH4 fluxes across the Arctic landscape. Wet sedge-dominated tundra exhibits particularly high rates of CH4 flux due to the presence of aerenchyma and therefore, plant-mediated transport of CH4. Yet the response of CH4 to future CO2 concentrations is still largely uncertain. Model predictions assumed that elevated CO2 (eCO2) will increase primary production and, as a result, CH4 emissions, but this has been poorly tested given the challenges of conducting eCO2 experiments in the Arctic. To address this knowledge gap, we tested the response of CH4 fluxes in soil and vegetation cores from a wet-sedge tundra ecosystem in Alaska to eCO2. The eCO2 stimulated plant productivity, but did not increase CH4 emissions. We think that carbon substrate availability is not limiting CH4 emissions from tundra soils because there is already substantial soil carbon present. Therefore, even an increase in plant productivity will not necessarily result in increased tundra CH4 emissions. Model predictions should consider the soil carbon storage in different ecosystems when predicting the increase in CH4 loss with elevated CO2.