Agroforestry systems (AFS) play a major role in the sequestration of carbon (C). The objectives of this study were to quantify the organic C stocks in the above- and below-ground tree biomass and in the soil in a cattle-farming system with live fences (CFSLF) of Gliricidia sepium and to compare the levels with those of a cattle-farming system based on a grass monoculture (CFSGM). The methodology included a forest inventory in nine randomly assigned plots and the destructive sampling of G. sepium 32 trees, measuring for each tree the diameter at breast height (DBH), stem height, total tree height, branch weight, leaf weight and coarse root weight. In addition, we measured grass biomass, collected litterfall and collected soil samples at depths of 0–10, 10–20 and 20–30 cm in the plots. A logarithmic model was developed to quantify the above- and below-ground tree biomass. The soil organic matter was determined by the dry combustion method. The total carbon stored in the CFSLF was 119.82 Mg C ha-1, with the G. sepium trees contributing 5.7 % of the total C (6.48 Mg C ha-1). The CFSGM stored 113.34 Mg C ha-1. The grass biomass stored 15.32 Mg C ha-1 year-1 in the CFSGM and 15.68 Mg C ha-1 year-1 in the CFSLF, and the litterfall in the CFSLF stored 0.205 Mg C ha-1 year-1. Despite the modest contribution of G. sepium trees to the C storage, the total carbon accumulated in the CFSLF and CFSGM was similar.