This work reviews historical contributions to the conceptualization of narcissism and Narcissistic Personality Disorder (NPD), including its evolution as a clinical diagnosis within the DSM classification of mental disorders. It focuses on the complexity of Narcissistic Personality Disorder and the importance of defining it as a continuum ranging from normal to abnormal personality expression. In this continuum, the authors identify two typical features, overt or grandiose and covert or vulnerable narcissism. Then, authors consider a wide variety of challenges that contribute to worse outcomes in therapies with NPD patients. Only few theoretical approaches have advanced treatments targeting NPD and hardly any of these treatments were tested in randomized controlled trials. Treating persons with PN, or with NPD is a challenge to clinicians as sound empirical evidence on how to treat them is lacking. The lack of empirically supported treatments has highlighted the need to provide some principles of “good clinical practice”, in line with the idea of a more integrated approach to the treatment of personality disorders.