Direct functionalization of 1,2-azaborines to construct B−C bonds remains challenging. Here, we report a Pdcatalyzed B−H aryl/alkenylation reaction of 1,2-azaborines. The method provides a general platform to access diverse boronsubstituted 1,2-azaborine compounds (>60 examples). The synthetic utility is highlighted through the late-stage modification of bioactive molecules, as well as the preparation and transformations of the 10 B-enriched 1,2-azaborine product and the synthesis of four BN isostere analogues of bioactive molecules. And the reaction mechanism is also explored and discussed.