China's outward foreign direct investment (OFDI) has emerged as a critical driver of economic development in Belt and Road (B&R) countries. However, its role in fostering agricultural productivity growth in the region remains underexplored. This study investigates the relationship between China's OFDI and agricultural productivity in 58 B&R countries from 2003 to 2021. Utilizing panel data, we quantitatively assess agricultural productivity while incorporating the influence of Chinese OFDI. Furthermore, the analysis distinguishes between high-income and middle- to low-income countries, offering a nuanced understanding of differential impacts. The results indicate that China's OFDI significantly enhances agricultural productivity across the region, with a particularly pronounced effect in middle- and low-income countries. This suggests that Chinese investments are more impactful in countries with lower income levels, underscoring their critical role in addressing disparities and promoting sustainable agricultural development. The findings provide actionable insights for policymakers in China and B&R countries, emphasizing strategies to deepen investment collaboration and advance agricultural sustainability, food security, and nutrition outcomes.