Observations of carbon dioxide (CO2) flux with the eddy covariance technique were conducted at a burned boreal forest site five years after a wildfire and at a mature forest site in Interior Alaska to investigate the effects of wildfire on CO2 exchange in a boreal forest. Both gross primary productivity and ecosystem respiration were lower at the burned site. The lower amount of vegetation explains the lower gross primary productivity and ecosystem respiration at the burned site. The reduced soil organic layer at the burned site further explains the lower respiration. On an annual basis, the five-year-old burned site was a CO2 sink, which indicated earlier recovery of CO2 exchange compared to other burned boreal forests in North America reported in the literature. The quick recovery of net CO2 exchange is associated with constrained heterotrophic respiration, rather than recovery of vegetation. Burn severity can be a key variable in determining CO2 exchange during the early stage of succession after wildfire.