Recent research shows that the combined contributions of deforestation, forest degradation and peat land emissions account for about 15 of greenhouse gas emissions. The REDD policy which preserves forests and values standing forests, enables substantial emission reductions. Since agricultural production and area expansion is a primary driver of tropical deforestation, REDD policies might limit the expansion possibilities of agricultural land use and therefore influence competitiveness of the agricultural sector, agricultural prices, trade patterns, agricultural production and therefore food security in the world. This paper studies the impact of REDD policies on the agri-food sector and food security with a global CGE model called MAGNET using a scenario approach. It focuses on the restrictions on agricultural land expansion within the REDD policy package. Simulation results show that REDD policies start to affect the agri-food sector in some lower developed countries if more than 15 of potentially available agricultural areas are protected from deforestation. A stringent REDD policy that protects 90 of land reserves that could potentially be used for agriculture production results in a global real agricultural price increase of almost 7.6, and a worldwide agricultural production decrease of 1.7. Regional differences are large, with real agricultural price changes ranging from 4 in North America to about 24 in Sub-Saharan Africa and South-East Asia. Food access rapidly deteriorates for low-income population in these regions in the case of high forest protection levels. Compensatory payments are necessary from a food security point of view if the level of forest protection increases. Our results indicate that from a food security perspective REDD policy should stop short of trying to protect more than 40 of global carbon if the compensation mechanism is not effectively implemented within REDD.