Rhodium-alloyed catalysts with both high activity and stability hold great promise for the hydroformylation of alkenes. Here, we report a rhodium–cobalt alloy assembled on hexagonal boron nitride nanosheets with abundant N vacancies through a simple one-pot impregnated approach (RhCo/dh-BN), in which vacancies promote metal dispersion and alloy formation, and improve the performance of internal heterogeneous hydroformylation reaction. According to FTIR, XRD, BET, TEM and EPR characterization suggest that N vacancies are constructed on boron nitride and RhCo alloy anchors, while XPS and STEM are used to characterize the structural and electronic properties as well as the morphology of the RhCo alloy. RhCo/ dh-BN exhibits good catalytic activity over a wide substrate scope for various aliphatic and aromatic alkenes including internal and terminal ones. As an example, for the 2-octene hydroformylation reaction, the nonanal yield is 97% with a TOF of 923 h−1. In addition, the catalyst could be reused up to five times under the same reaction conditions without loss of activity.