Introduction: The present study conducted to explain self-differentiation according to attachment styles and alexithymia.Method: This is a descriptive–correlational study in which 325 students were selected through stratified random sampling. To gather required data self-differentiation questionnaire (DSIR- R), Hazan and Shower attachment questionnaire plus alexithymia inventory (FTAS-20) were used. Data analysis was also conducted by statistical methods of correlation and regression.Results: Findings showed that there was positive and significant relationship between safe attachment style and self-differentiation. There was a negative relationship between aversive attachment style and self-differentiation either. Results were also suggestive of a negative relationship between alexithymia and self-differentiation. All things considered, aversive attachment style, alexithymia and safe attachment style can predict self-differentiation.Conclusion: According to the results, safe attachment style as well as emotional expression are the main factors contributing to high level of self-differentiation.