The present study aims at empirically exploring subtypes of narcissistic personality disorder (NPD), based on patient descriptors of the psychotherapeutic process. Subtype identification and characterization of NPD is central, in particular, to increase diagnostic precision, linking categorical and dimensional conceptualizations of psychopathology, and to individualize treatments. A total of N = 161 patients diagnosed with NPD undergoing clarification-oriented psychotherapy were included in the present reanalysis of a naturalistic pre-post process-outcome study. At three crucial time-points of the therapy (Sessions 15, 20, and 25), the patient's in-session quality of content, process, and relationship are assessed using intensive video- and audio analyses. Levels of psychopathology were assessed using self-reported questionnaires. Data were analyzed using longitudinal nonparametric analysis. Based on in-session processes across three time-points, a two-subtype solution was retained (optimal vs. suboptimal process qualities). Optimal process quality of time was linked with the intensity of narcissistic symptoms; suboptimal process quality was linked with a variety of general symptom loads and problematic personality traits. The two empirical subtypes were predicted by the quality of real-life functioning with an accuracy of more than 92% and were partially associated with outcome. NPD may be empirically differentiated between patients engaging in optimal psychotherapy process versus those who engage in suboptimal psychotherapy process. This differentiation has reliable clinical predictors at the outset of treatment. The present study has implications in terms of personalizing psychotherapy for patients presenting NPD, or pathological narcissism. (PsycInfo Database Record (c) 2021 APA, all rights reserved).