<p>This study examines how multidimensional urbanization affects agricultural carbon emission intensity (AEI) across 47 Belt and Road countries from 2000 to 2020, using a panel spatial Durbin quantile model with country and year fixed effects and Kelejian–Prucha instruments for the endogenous spatial lag. Four findings emerge. (1) Population urbanization carries no effect on AEI on average; a positive marginal effect surfaces only in economies where the agricultural labour transition is largely complete, and the relationship stays statistically unresolved earlier in the transition. (2) Economic urbanization, proxied by nighttime-light intensity, raises AEI across the conditional distribution, with the sign holding across three spatial weight matrices and on the post-2010 subsample. (3) Land urbanization mitigates AEI within countries at the lower tail of the conditional distribution, but cross-border displacement largely offsets this gain at the regional level, leaving the average total effect indistinguishable from zero. (4) Once country effects are absorbed the spatial autoregressive parameter on AEI is negligible; transmission instead runs through neighbours’ urbanization, a brighter neighbouring economy lowering domestic AEI and a more built-up neighbouring landscape raising it.</p>