Herein, the origin of the diastereoselectivity of N-heterocyclic carbene (NHC)-catalyzed cross-benzoin reactions between an α-amino aldehyde and furfural was studied by density functional theory. The computational results showed that the reaction proceeded through four steps:nucleophilic addition of NHC onto furfural, formation of a Breslow intermediate, cross-coupling reaction between Breslow intermediate andα-amino aldehyde, and dissociation of the catalyst. The cross-coupling was identified as the diastereoselectivity-determining step, with the R-configured product generated preferentially. Non-covalent interaction (NCI) analysis showed that the C-H???O and C-H???F interactions were responsible for determining the diastereoselectivity.