In this article intellectual hypermaturity, insofar as it has its roots in sexuality, is examined in regard of its constitution, functions and consequences. Following Ferenczi, it is envisaged as the visible aspect of early narcissistic self-splitting which is formed in reaction to the seduction of adult sexuality, thereby hindering the development of infantile sexuality. Based on clinical work with an adolescent, the authors show how, once conditions have been created that favour the emergence of the negative transference, the initiation of the pubertal process and the intensification of the transference are accompanied by the gradual dismantling of intellectual hypermaturity, allowing the buried part of the splitting to appear, albeit with violence. The presence of a non-intrusive therapeutic environment allows the constitution of new narcissistic foundations, on the basis of which the patient can confront sexuality and the elaboration of the Oedipus complex without resorting to hypermaturity as a defence.