Narcissistic personality disorder has been challenging to diagnose in psychiatric and general clinical practice. Several circumstances and personality factors related to the nature of pathological narcissism and NPD contribute. NPD is usually a moderately impairing condition, often accompanied by specific capabilities and high level of functioning. Comorbidity of other urgent and recognizable psychiatric conditions, such as mood and substance use disorders or suicidality, can override even significant narcissistic personality functioning. Patients' limited ability to recognize own contribution to problems or impact on other people, their hypersensitivity and defensive reactivity, and compromised ability for self-disclosure, self-reflection, and emotional empathy can make initial evaluations difficult. The aim of this study is to integrate recent clinical and empirical knowledge on the underpinnings of pathological narcissism and narcissistic personality functioning, and distinguish narcissistic self-regulatory patterns that are affecting diagnostic traits. A more flexible, exploratory, and collaborative diagnostic process is proposed that integrates the patients subjective experiences and interpersonal functioning in terms of self-regulation, agency, and traits in a way that is informative and meaningful for both the patient and the clinician.