Canada has a quarter of the world's peatlands accounting for an estimated 150 Gt of stored carbon. While over 98% of Canadian peatlands are intact, agriculture has been estimated as accounting for the greatest peatland disturbance by area. Greenhouse gas (GHG) emissions from peatland agriculture can contribute a large proportion of national anthropogenic emissions for some countries. In Canada, estimates of GHG emissions from cultivated peat soils are incomplete. Improved accounting of these GHG emissions is required to inform decisions about where to deploy ecological restoration projects and where to allow future agricultural expansion as climate warms. Compiled studies that measured GHG fluxes from agricultural peat fields in Canada resulted in mean emissions factors of 5.1 t CO2e ha−1 year−1, −0.12 kg CH4 ha−1 year−1, and 14.3 kg N2O-N ha−1 year−1 for carbon dioxide, methane, and nitrous oxide, respectively. Combining these values with a compilation of estimates of agricultural peatland disturbance area in Canada, GHG emissions estimates in Canada arising from peatland converted to agriculture remain highly uncertain, ranging from 1.4 to 35 Mt CO2e year−1, with a median value near 18 Mt CO2e year−1. The largest contributor to this wide range of estimates is uncertainty peatland area affected, indicating an urgent need to improving mapping of organic soils under agriculture in Canada. To help guide decision-making in Canada, we recommend a network of research stations across a range of agricultural management intensities and climate regions for monitoring hydrological conditions and GHG exchange on organic soils affected by agriculture.