This study aims to quantify the biomass and carbon stock in a crop of physic nut Jatropha curcas in Viçosa-MG at age three years. For biomass quantifi cation, the direct or destructive method was applied to sample plants selected according to height, crown diameter and number of branches. For the determination of dry biomass in the fi eld, the proportionality method was used. The determination of total carbon content was done in the Laboratory of Forest Soils of the Federal University of Viçosa, and the estimation of CO 2 equivalent was based on the 3.67 factor. The carbon stock found in the third year of cultivation was 4.182 tC.ha -1 (15.349 tCO 2-e .ha -1) and the mean annual increment (MAI) was 1.394 tC.ha -1 .year -1 . Results revealed that the potential carbon increment in the physic nut crop is similar to values found in other crops and natural forests yet lower than in eucalyptus crops. total foi determinado no laboratório de solos fl orestais da Universidade Federal de Viçosa e a estimativa do CO 2 equivalente pelo fator 3,67. O estoque de carbono encontrado para o terceiro ano da cultura do pinhão manso foi de 4,182 tC.ha -1 (15,349 tCO 2-e .ha -1) e o incremento médio anual (IMA) de 1,394 tC.ha -1