The recent increase in cases of depression with a narcissistic tendency, especially among young individuals, has been pointed out. When the narcissistic tendency is conspicuous, patients may be treated for a personality disorder or pervasive developmental disorder, and not for a mood disorder. A case is described of a man in his late twenties who developed depression due to his failure in research work and job hunting, and, after a time, due to the break off of his engagement with his fiancée, manifested with narcissistic symptoms including an exaggerated opinion of himself, a sense of entitlement, interpersonal exploitation, lack of empathy, strong feelings of envy, and an extrapunitive tendency. He was regarded at the start of treatment as having narcissistic personality disorder. However, persevering treatment, mainly with supportive psychotherapy and pharmacotherapy including antidepressants (high dose of maprotiline combined with low dose of mirtazapine), sodium valprote and aripiprazole, finally improved not only his depressive symptoms, but also the symptoms regarded as a deriving from a personality disorder. He presented fierce anger and aggression regarded as a mixed state, and showed the rapid improvement in his depressive state after hospitalization, which we considered to show potential bipolarity. We diagnosed the patient with narcissistic depression, emphasizing the aspect which suggested a mood disorder, such as the episodic presence of narcissistic symptoms as long as a depressive state resided, his circular, recursive discourse, and his potential bipolarity. To accurately evaluate the aspect of mood disorders which patients appearing to show personality disorders have, it is considered useful to grasp a patient's condition from the viewpoint of a personality structure and viable dynamics. From a therapeutic standpoint, we suggest the importance of simple but persevering psychotherapy and a sufficient quantity of antidepressant medication for patients with depression, even if they are thought to have a personality disorder.