To evaluate the associations between DSM‐5 alternative model of personality disorder dysfunctional personality domains and the clinician’s ratings of non‐suicidal self‐injury (NSSI) severity, a sample of consecutively admitted Italian adolescent inpatients (N = 100) were administered the Italian translations of the DSM‐5 Clinician Rating Scale‐NSSI (CRS‐NSSI), the Personality Inventory for DSM‐5 (PID‐5), the Structured Clinical Interview for DSM‐IV Axis II Personality Disorders, Version 2.0 (SCID‐II) and the Children’s Depression Inventory (CDI). Bivariate association analyses showed that PID‐5 negative affectivity scores and CDI total score were significantly associated with CRS‐NSSI ratings. PID‐5 negative affectivity score proved to be a significant predictor of the CRS‐NSSI score even when the effect of the CDI total score was held constant. Our results highlighted that specific risk factors for NSSI severity may be identified even among NSSI adolescents. © 2019 John Wiley & Sons, Ltd.