Background: Temperament and character traits of adolescents with nonsuicidal self-injury disorder (NSSI) might differentiate those-with and without comorbid borderline personality disorder (BPD). Methods: Participants were 57 female adolescents with NSSI disorder without BPD (NSSI-BPD), 14 adolescents with NSSI disorder and BPD (NSSI + BPD), 32 clinical controls (CC), and 64 nonclinical controls (NC). Temperament and character traits were assessed with the Junior Temperament and Character Inventory, and impulsivity with the Barratt Impulsiveness Scale and a Go/NoGo task. Results: Adolescents with NSSI disorder scored significantly higher on novelty seeking and harm avoidance and lower on persistence, self-directedness, and cooperativeness than CC. The NSSI + BPD group scored even higher than the NSSI-BPD group on novelty seeking and harm avoidance and lower on persistence and cooperativeness (d >= 0.72). Adolescents with NSSI reported higher levels of impulsivity than the CC and NC group. However, this difference was not found in a Go/NoGo task. Conclusions: The results provide further evidence for a distinct diagnostic entity of NSSI disorder.