Carbon (C) sequestration through the implementation of agroforestry practices is identified as one of the major strategies in the reduction of carbon dioxide (CO₂) emissions from the agricultural sector. The objective of this study was to examine the soil organic carbon (SOC) sequestration potential of major shelterbelt species, including green ash (Fraxinus pennsylvanica), hybrid poplar (Populus spp.), Manitoba maple (Acer negundo), white spruce (Picea glauca), Scots pine (Pinus sylvestris), and caragana (Caragana arborescens), ranging in age from 5 to 63 yr. Soil samples (0–50 cm) were collected for six major shelterbelt species and adjacent agricultural fields, and SOC concentration was determined. Shelterbelts had a significantly higher amount of SOC compared with adjacent agricultural fields, with an average difference of 18.6 Mg C ha^-1 in the top 50 cm soil. An additional 3–8 Mg C ha^-1 was contained in the tree litter layer. Younger shelterbelts (age less than 20 yr) tended to lose SOC in the early years of shelterbelt establishment. However, the SOC accrual was positively related to shelterbelt stand age. Besides stand age, other shelterbelt stand characteristics, including tree height and diameter, crown width, and amount of surface litter, were also positively correlated with the increase in SOC concentration. The findings of this study support the hypothesis that shelterbelts can lead to a significant amount of SOC sequestration in agroecosystems.