: This study examines non-suicidal self-injury (NSSI) behavior, its functions and associated factors like childhood trauma, alexithymia, empathy, and emotion regulation, in adolescents suffering from depression.: The study sample consisted of 67 adolescents; 11 boys (mean age = 14.94 ±1.45) and 56 girls (mean age = 14.72 ±1.48), all with major depressive disorder. Standard tests and measurements were used for data collection, including Beck Depression Inventory for identifying depression symptoms; Brief Symptom Inventory for screening psychiatric symptoms; Inventory of Statements About Self Injury (ISAS) to identify the lifetime frequency and functions of NSSI in subjects; Childhood Trauma Questionnaire to evaluate sexual, physical, and emotional abuse plus childhood neglect; Toronto Alexithymia Scale to assess difficulties in identifying and/or describing feelings; Basic Empathy Scale to measure empathy levels within the framework of basic emotions; and the Difficulty of Emotion Regulation Scale to determine the awareness and clarity of emotional response.: It was found that 64.1% of adolescents studied have had at least one NSSI to date. The most frequent intrapersonal functions associated with NSSI were Affect Regulation and Marking Distress, and the most common interpersonal functions were Toughness and Interpersonal Boundaries. According to a correlation analysis with ISAS scores, Affect Regulation was associated with obsession-compulsion, anxiety, difficulty identifying feelings and clarity scores. Marking Distress, generating a physical sign of feeling awful, was positively associated with Paranoid Ideation scores and negatively associated with Emotional Neglect scores. The Interpersonal Boundaries was positively associated with Childhood Physical Abuse and Impulse scores.: NSSI is realized by different functions in the intrapersonal and interpersonal areas in adolescents with depression. Emotion regulation abilities, alexithymia, and childhood trauma are also associated factors or functions of NSSI.