The present invention concerns a process for hydrocyanating ethylenically unsaturated organic compounds to compounds containing at least one nitrile function. It relates more particularly to the hydrocyanation of diolefins such as butadiene or of substituted olefins such as alkenenitriles, for instance pentenenitriles. According to the process of the invention the reaction is implemented in the presence of a metal complex catalyst comprising a transition metal such as nickel and an organic ligand.