Agriculture has the potential to contribute significantly to cost-effective greenhouse gas (GHG) mitigation potential (Smith et al. 2007a; 2008), comparable at a range of future carbon prices to the economic potential in the industry, energy, transport, and forestry sectors (Barker et al. 2007). Based on carbon prices of US$20-100/t CO2e, the agricultural mitigation potential from all gases is ~1, 500-4, 300 megatonnes (Mt) CO2e/yr, or 25-78% of the technical potential of ~5, 500-6, 000 Mt CO2e/yr (Smith et al. 2007a; Smith and Olesen 2010). The annual economic mitigation potential is estimated to be worth between US$32 thousand million and US$420 thousand million. About 70% of the potential arises from developing countries with a further 10% from countries with economies in transition (Trines et al. 2006). Despite mitigation’s significant economic potential, however, most farmers in developing countries are smallholders who will have to prioritize farm practices that enhance their food and livelihood security. This implies that to achieve the economic mitigation potential in developing countries, mitigation measures will need to support improved food production, especially that which is adapted to the changing climate, and profitability. Such practices are often referred to as “win-win” options, and strategies to implement such measures can be encouraged on a “no regrets” basis (Smith & Powlson, 2003), i.e., they provide other benefits even if the mitigation potential is not realized. For many farmers, mitigation payments will only be co-benefits to the main enterprise of food production. The aim of this chapter is therefore to identify the synergies of mitigation with food security and improved livelihoods to support viable mitigation options for farmers in developing countries. We focus on agronomic adaptation of crops and livestock as an indicator of food security. Synergies between mitigation and food security have been examined elsewhere (Mann et al. 2009; see also McCarthy et al.). Below we discuss the range of mitigation options, the relationship of miti- gation to adaptation and livelihoods, and a framework for further testing of synergies.