A facile cleavage reaction of the germanium–carbon bond of (germylmethyl)amine derivatives to give a germyl anion and an azomethine derivative was developed. The effects of substituents such as phenyl, benzyl, and ethyl groups on the germanium and nitrogen atoms of the (germylmethyl)amine derivatives on the cleavage reaction, were investigated. The mechanism was also investigated based on the stereochemistry