Introduction: Identification in teens is not an automatic and voluntary events but can be influenced by various intra and inter personal, and social factors such as family atmosphere and its dynamics relations and the concept of self-differentiation. This study was conducted to determine process of self-differentiation in teenagers by the cohesion and flexibility in the family. 
Methods: This research is a correlational study and population consisted of all ninth to twelfth grades male students in high school in Tehran in 2015-2016 school calendar. Of these samples, 231 participant were selected by multistage cluster sampling, and then they responded to the scales of cohesion and family flexibility and self-differentiation. Data was analysed by descriptive and inferential statistical methods. (regression analysis)
Results: According to the findings, higher self-differentiation correlates with higher cohesion and flexibility. So cohesion and flexibility can determine and predict self-differentiation in male teens.
Conclusions: These findings show that if parents can regulate cohesion and flexibility as dimensions of their family relationship they can help their children to reach a proper self-differentiation and decrease the risk of problems may they have in their life. Meanwhile because this study is limited to male student in a city, more studies in this field should confirm our results.