Aim and Background: Based on the theories of etiology of self-injury behaviors, several psychological and social multivariate models have been investigated to predict self-injury behaviors in adolescents. This study aimed to investigate the mediating role of self–criticism and distress tolerance in relationship between attachment styles and non-suicidal self-injury behaviors in adolescents.

Methods and Materials: This study was a descriptive-correlational study with structural equation modeling approach. The statistical population consisted of all high school students in Kashmar city in the years 2018-2019. Initially, a sample of 700 students was selected among all high school students were selected by multistage cluster sampling, but the final analysis was performed on 292 students who reported at least one experience of non-suicidal self-injury behaviors. Data were collected using Deliberate Self–Harm Inventory (DSHI), Childhood Attachment to Each Parent Scale (CAEPS), Distress Tolerance Scale (DES) and Forms of-Self–Criticism/Attacking & Self-Reassuring (FSCRS) and were analyzed in SPSS and LISREL software by using structural equation modeling.

Findings: The results showed that the relationship between attachment styles and non-suicidal self-injury behaviors mediated by self-criticism and distress tolerance. The amount of fit indices of GFI, CFI, NFI, IFI, NNFI, AGFI, RFI and RMSEA were equal to 0.94, 0.93, 0.90, 0.93, 0.90, 0.90, 0.89 and 0.071, respectively. The results indicate that the proposed model fits the data well. The findings of the study showed that 34% of the observed variance in non-suicidal self-injury behaviors can be explained through a combination of parent attachment, self-criticism and distress tolerance.

Conclusions: The findings of this study confirmed the mediating role of self-criticism and distress tolerance in the relationship between attachment styles and non-suicidal self-injury behaviors. Thus, it seems necessary for experts, therapists and planners when working with adolescents and specifically in counseling and treatment centers to consider the role of these mediating variables.