Introduction: Reducing agricultural carbon emissions is central to China’s carbon-neutrality goals, yet the effectiveness and operating mechanisms of green finance in supporting low-carbon agricultural production remain insufficiently understood. This study examines the effects, mechanisms, regional heterogeneity, and spatial spillovers of green finance on agricultural carbon emissions. Methods: Using provincial panel data for China from 2007 to 2024, we estimated two-way fixed-effects and spatial Durbin models within the technology–organization–environment framework. We used mechanism, moderating-effect, robustness, and instrumental-variable analyses to examine transmission channels, contextual conditions, model sensitivity, and endogeneity. Results: A one-unit increase in the green finance index corresponded to an approximately 19% reduction in agricultural carbon emissions. Green finance reduced emissions by promoting agricultural green technological innovation and strengthening agricultural socialized services, while digital infrastructure enhanced its carbon-reduction effect. The effect was stronger in major grain-producing regions and areas exposed to higher agricultural natural risks. Agricultural carbon emissions exhibited positive spatial dependence. Green finance produced a statistically significant local direct effect, but we found no robust evidence of cross-regional spillovers. Discussion: Green finance supports agricultural decarbonization through locally embedded technological and organizational capacities. Policies should align green financial instruments with regional production functions and natural-risk conditions, strengthen digital infrastructure and agricultural service systems, and improve cross-regional coordination.