Selfinjurious behaviors among adolescents represent a significant mental health concern, as they are closely associated with emotional dysregulation, psychological distress, and an increased risk of suicidal behaviors. Adolescence is a developmental period marked by rapid biological, emotional, and social changes, which may heighten vulnerability to maladaptive coping strategies such as nonsuicidal selfinjury. Previous research has consistently emphasized the role of familyrelated factors in the emergence and maintenance of selfinjurious behaviors, particularly in collectivist cultures where family relationships play a central role in adolescents’ psychological adjustment. Among these factors, perceived interparental conflict and triangulation have been identified as critical sources of familial stress that may undermine adolescents’ emotional security and contribute to maladaptive behavioral outcomes.Perceived interparental conflict refers to adolescents’ subjective appraisal of the frequency, intensity, and resolution of conflicts between parents. Exposure to chronic and unresolved parental conflict has been linked to emotional insecurity, internalizing and externalizing problems, and selfdestructive behaviors. Triangulation, grounded in family systems theory, occurs when adolescents are emotionally or behaviorally drawn into parental conflicts, often being pressured to take sides or mediate disputes. Such involvement places adolescents in developmentally inappropriate roles and increases emotional burden and stress. Despite growing interest in these constructs, the mechanisms through which perceived interparental conflict and triangulation influence selfinjurious behaviors remain insufficiently examined, particularly within nonWestern cultural contexts.Family functioning, encompassing dimensions such as cohesion and Adaptability, may serve as a key mechanism in this process. Family cohesion reflects the emotional bonding among family members, whereas family Adaptability refers to the family’s capacity to adapt roles, rules, and power structures in response to situational demands. Dysfunctional family functioning may intensify the adverse effects of parental conflict and triangulation, thereby increasing adolescents’ vulnerability to selfinjurious behaviors. However, empirical studies examining these relationships simultaneously within a comprehensive structural model are limited, especially among Iranian adolescent girls.Accordingly, the present study aimed to predict selfinjurious behaviors among adolescent girls based on perceived interparental conflict and triangulation, with an emphasis on the mediating role of family functioning. It was hypothesized that perceived interparental conflict and triangulation would be positively associated with selfinjurious behaviors, both directly and indirectly, and that family functioning would mediate these relationships.This descriptivecorrelational study was conducted using structural equation modeling (SEM). The statistical population consisted of female high school students in the second level of secondary education in Khorramabad during the 2022–2023 academic year. A total of 350 students were selected through multistage cluster sampling. Data were collected using the Family Adaptability and Cohesion Evaluation Scale- III (FACES III), Self Harm Invetory (SHI), the Adolescent Triangulation Scale (TAS), and the Adoloscent’s Perception of Interparental Conflict Scale (APIC). All instruments demonstrated acceptable reliability in the present sample. Data analysis was conducted using structural equation modeling, Structural equation modeling was selected as the primary analytical approach due to its ability to simultaneously examine complex relationships among latent variables and to test both direct and indirect pathways within a single comprehensive model , and model fit was evaluated using the normed fit index (NFI), the standardized root mean square residual (SRMR) and GoodnessofFit (GOF). The results indicated that selfinjurious behaviors were positively and significantly associated with perceived interparental conflict, triangulation, and family functioning (p < .01). Higher levels of perceived interparental conflict, triangulation, and dysfunctional family functioning were related to increased selfinjurious behaviors. Furthermore, family functioning played a significant mediating role in the relationship between perceived interparental conflict and selfinjurious behaviors. However, family functioning did not mediate the relationship between triangulation and selfinjurious behaviors. In explaining the non‑significant mediating role of family functioning, it should be noted that the relationship between triangulation and the adaptation dimension of family functioning was not statistically significant. Since the establishment of statistical mediation requires a significant association between the independent variable and the mediator, the lack of significance in this path prevented confirmation of the mediating role of family functioning. This finding may indicate that triangulation, as a pattern of emotional entanglement and unstable alliances within the family system, does not necessarily lead to measurable changes in overall family adaptability. Under such conditions, the effects of triangulation on self‑injurious behaviors may operate more strongly through direct emotional strain, loyalty conflicts, and emotional insecurity in adolescents rather than through broader structural or adaptive family processes. Nevertheless, given the cross‑sectional design of the present study, this interpretation should be considered with caution and within the methodological limitations of the research.These findings highlight the central role of family dynamics in understanding selfinjurious behaviors among adolescent girls. The results suggest that perceived interparental conflict may influence selfinjurious behaviors partly through its impact on overall family functioning. In contrast, the effects of triangulation on selfinjurious behaviors appear to be more direct and less dependent on broader family functioning patterns. From a clinical perspective, these findings underscore the importance of familybased preventive and therapeutic interventions aimed at reducing adolescents’ involvement in parental conflicts and improving family functioning. Strengthening emotional bonds within the family and promoting adaptive interaction patterns may help reduce vulnerability to selfinjurious behaviors among adolescent girls.Future research is recommended to employ longitudinal designs and include male adolescents to further clarify causal pathways and enhance the generalizability of the finding.