A chemoselective phosphine-catalyzed cyanoacylation of α-dicarbonyl compounds is reported. Under the catalysis of P(NMe₂)₃, the cyanoacylation of α-dicarbonyl compounds such as isatins, α-keto esters, and α-diketones with acyl cyanides exclusively proceeds under very mild conditions, affording a wide range of cyanohydrin esters bearing one quaternary stereocenter in moderate to excellent yields. It represents the first phosphine-catalyzed cyanoacylation of α-dicarbonyl compounds and also provides a general method to prepare fully substituted cyanohydrin esters.