Shelterbelts provide an opportunity for carbon (C) sequestration and have the potential to mitigate agricultural greenhouse gas (GHG) emissions. However, the influence of shelterbelts on GHG emissions at the farm scale is poorly understood. We estimated the potential of three shelterbelt tree species: hybrid poplar, white spruce, and caragana at five planting densities, to reduce GHG emissions in a model farm (cereal–pulse rotation). The Holos model, a Canadian farm-level GHG calculator developed by Agriculture and Agri-Food Canada, was used to estimate shelterbelt effects on farm GHG emissions over a 60 yr time frame. The planting densities of the shelterbelts represented 0%, 0.5%, 1.0%, 3.0%, and 5.0% of the total area of an average (688 ha) Saskatchewan farm. The greatest reduction in farm GHG emissions was estimated for hybrid poplar (23.0%) followed by white spruce (17.5%) and caragana (8.2%) — all at the highest planting density. The GHG mitigation by the shelterbelts was attributable primarily (90%–95% of GHG reduction) to C sequestration in tree biomass and in soil organic carbon (SOC) pools, with the remainder due to lower N₂O, CH₄ emissions, and a reduction in farm energy use. The GHG estimates from Holos agree with field measurements and suggests that species selection will be important for maximizing C sequestration and GHG mitigation potential of shelterbelt systems; conversely, shelterbelt removal from the agricultural landscape suggests an increase of on-farm GHG emissions.