alpha-Diazoesters were discovered to be good electrophiles in a catalytic asymmetric alpha-functionalization of ketones for the first time. This reaction also provided a direct and efficient method for C-N bond formation with excellent yields (up to 98%) and enantioselectivities (up to 99% ee) under mild conditions. The application of the electrophilicity of alpha-diazoesters opens up a novel way to access the diversity of diazo chemistry.