<p>Exploring how green transition of farmland use affects grain production capacity is critical for promoting the green development of agriculture and ensuring national food security. This study used panel data from 31 Chinese provinces (metropolises) spanning 2000 to 2020 to investigate the spatial effects of green transition of farmland use on grain production capacity using a spatial Durbin model. The results showed an overall increasing trend for the green transition of farmland use and grain production capacity, with significant regional differences. The total effect coefficient of green transition of farmland use on grain production capacity was 0.988, among which the direct and spatial spillover effects were 0.790 and 0.198, respectively. This indicates that enhancing local green transition of farmland use is not only a core endogenous driver for promoting the growth of local grain production capacity. It can also generate a positive spillover effect on the grain production capacity of neighboring regions through the horizontal strategic interactions among local governments, factor mobility, and resource sharing. The direct and total effects of green transition of farmland use on grain production capacity were significantly positive in four regions. However, the spillover effects were negative in the eastern and central regions but positive in the western and northeastern regions, demonstrating regional heterogeneity. All regions should integrate regional resource endowments and agricultural development foundations, promote the green transition of farmland use in a differentiated manner, and thereby drive the synergistic improvement of this transition and grain production capacity.</p>