Peatlands are a highly effective natural carbon sink. However, the future of the carbon stored in these ecosystems is still uncertain because of the pressure they undergo. As estimation of the peatland carbon balance shows whether the system functions as carbon sink or source. La Guette peatland is a temperate Sphagnum-dominated peatland invaded by vascular plants, mainly Molinia caerulea. The studied site was hydrologically disturbed for years by a road crossing its southern part and draining water out of the system. Our aim was to estimate the main carbon fluxes and to calculate the carbon balance at the ecosystem scale. To reach this goal, CO 2 and CH 4 fluxes, DOC content as well as environmental variables were measured monthly for 2 years on 20 plots spread across the site to taking into account spatial variability. The peatland carbon balance was estimated using empirical models. Results showed that the CO2 fluxes were above 1000 gC m-2 yr-1. In 2013 and 2014 the peatland was a net C source to the atmosphere with an emission of 220±33 gC m-2 yr-1. These results provided evidence that restoration should be performed in order to reduce the water losses and favour the Sphagnum-dominance of this peatland.