The knowledge about dynamics of soil organic carbon (SOC) accumulation and its controls are critical in understanding of the C cycling in forest ecosystems. Acacia mangium Willd. is one of the most important fast-growing afforestation tree species in Vietnam, providing significant ecological, economic, environmental, and social benefits. The existing studies offered information limited on the distribution and regulation of SOC in the A. mangium plantations. The primary purpose of this study was to explore the variation trend of SOC and its driving factors in an age-sequence of three A. mangium plantation stands in Changriec Historical -Cultural Forest, Southeastern region, Vietnam. The study was conducted to estimate SOC content and storage, and soil physicochemical characteristics of three different-aged (4-, 7-, 11-year-old stands) A. mangium plantations. The SOC content increased significantly from young to older stand, and its maximum concentration occurred in the topsoil layer and decreased continually with increasing soil depth. The SOC stocks increased significantly with the stand age. The SOC stocks showed obvious surface aggregation, with more than 60% of SOC distributed in the soil of 0-30 cm depth. The soil total nitrogen content and soil texture (i.e., soil silt content) were identified as the major factors controlling the SOC distribution. The other parameters (i.e., plant biomass, soil pH, bulk density, available nitrogen, total phosphorus, available phosphorus, total potassium, and available potassium) also significantly influenced the distribution of SOC. These findings suggest that afforestation with A. mangium can facilitate SOC accumulation, improve soil nutrient regimes, and