Although northern peatlands cover only 3% of the land surface, their thick peat deposits contain an estimated one-third of the world's soil organic carbon (SOC). Under a changing climate the potential of peatlands to continue sequestering carbon is unknown. This paper presents an analysis of 6 years of total carbon balance of an almost intact Atlantic blanket bog in Glencar, County Kerry, Ireland. The three components of the measured carbon balance were: the land-atmosphere fluxes of carbon dioxide (CO2) and methane (CH4) and the flux of dissolved organic carbon (DOC) exported in a stream draining the peatland. The 6 years C balance was computed from 6 years (2003–2008) of measurements of meteorological and eddy-covariance CO2 fluxes, periodic chamber measurements of CH4 fluxes over 3.5 years, and 2 years of continuous DOC flux measurements. Over the 6 years, the mean annual carbon was −29.7±30.6 (±1 SD) g C m−2 yr−1 with its components as follows: carbon in CO2 was a sink of −47.8±30.0 g C m−2 yr−1; carbon in CH4 was a source of 4.1±0.5 g C m−2 yr−1 and the carbon exported as stream DOC was a source of 14.0±1.6 g C m−2 yr−1. For 2 out of the 6 years, the site was a source of carbon with the sum of CH4 and DOC flux exceeding the carbon sequestered as CO2. The average C balance for the 6 years corresponds to an average annual growth rate of the peatland surface of 1.3 mm yr−1.