Soil organic carbon (SOC) sequestration is a key nature-based solution to mitigate climate change. Previous studies have highlighted its potential and the role of improve management practice, but many relied on static land-use assumptions or limited spatial data, overlooking socio-economic and climate-driven changes that affect land availability. This study assessed the global SOC sequestration potential of cropland and bioenergy land under three land-use pathways: business as-usual (BAU), a sustainable food system (FOOD), and a 2 °C climate target (2°). Our results show that both climate and food policies may influence SOC sequestration through land-use changes. Under the 2 °C scenario, large-scale expansion of bioenergy crops could increase SOC stocks by about 7% (∼9 Gt CO2). In contrast, the FOOD scenario achieves only modest SOC gains, slightly lower than BAU (−1.59 Gt CO₂). This because dietary shifts reduce pasture demand but do not significantly change cropland area, and bioenergy deployment is limited. While plant-based diets improve food system efficiency and reduce emissions, their SOC benefits are indirect and depend on how freed-up land is used for mitigation, such as afforestation or bioenergy production. Regions with significant bioenergy expansion—such as Latin America, reforming economies, and OECD/EU countries—show the highest SOC gains. Regions with large cropland areas, including the Middle East, Africa, and Asia, contribute 70% of the global potential. Moreover substantial SOC potential can be realized at a cost below $100 per ton of CO₂, highlighting SOC sequestration as a feasible and economically viable climate mitigation strategy. Our study findings underscore the trade-offs between food system transformation, land-use efficiency, and carbon storage, and emphasize that climate policies promoting bioenergy expansion can achieve substantial SOC gains, while dietary policies alone have limited impact if without strategic land management.