In this paper I shall describe the psychotherapeutic treatment of a 14-year-old boy, who suffered from mild Asperger's syndrome. This adolescent had a multiplicity of imaginary friends, which protected him from catastrophic feelings of loneliness and deadness, but at the same time interfered with the possibility of establishing meaningful relations with human beings. As the relationship with the therapist gradually gained the vitality and importance originally invested in his parallel fantasy world, the imaginary companions simultaneously faded away. His imagination then became more closely connected to inner reality and to creative processes. The psychoanalytic literature on imaginary companions is reviewed, and it is suggested that the concept of a self-protective device could be usefully applied to understanding the functions that this fantasy performed for the patient.