Enzymes create chiral microenvironments that may simultaneously generate several stereogenic centers in the same catalytic cycle, broadening the possibilities of biocatalysis. Benzaldehyde lyase (BAL) affords highly diastereoselective α-hydroxy-ketones by simultaneously performing ligation and kinetic resolution of a racemic aldehyde. Thus, to the well-known enantioselective BAL-carboligation of aldehydes (C–C bond formation), another property, namely diastereoselectivity, is added in this paper for the first time.