This article addresses the challenge of developing a ‘bottom-up’ marginal abatement cost curve (MACC) for greenhouse gas (GHG) emissions from UK agriculture. An MACC illustrates the costs of specific crop, soil and livestock abatement measures against a ‘business as usual’ scenario. The results indicate that in 2022 under a specific policy scenario, around 5.38 Mt CO2 equivalent (e) could be abated at negative or zero cost. A further 17% of agricultural GHG emissions (7.85 Mt CO2e) could be abated at a lower unit cost than the UK Government’s 2022 shadow price of carbon [£34 (tCO2e)−1]. The article discusses a range of methodological hurdles that complicate cost-effectiveness appraisal of abatement in agriculture relative to other sectors.