The first asymmetric synthesis of 3-amino-substituted isoindolinones was accomplished via cascade hemiaminal-heterocyclization-intramolecular aza-Mannich reaction of benzylamines and 2-formylbenzonitriles using chiral phase transfer conditions (PTC). A theoretical study of the enantioselective step provides a rationale for the mode of action of the best performing phase transfer catalyst and the observed face selectivity.