Background: The identification of positive family and personality factors affecting the reduction of negative outcomes in adolescent girls is important. Aims: This study aimed to study the family function and positive youth development to predict depression in adolescents. Method: The present study was a correlationaldescriptive design. The statistical population consisted of all secondary school female students (second period) in the city of Tehran who were studying in the academic year 2018-2019. So, 293 girl adolescents that were selected from 18th district of education regions by method was multi-stage cluster. According to the sample loss, 293 individuals were included in this study. To collect data, Geldhof et al. ’ s Positive Youth Development Scale(2014), the Epstein et al. ’ s Family Assessment Device(1983), and Kovacs and Beck’ s Child Depression Inventory(1977) were used. Data were analyzed by using SPSS24. Results: The results revealed that competence, confidence, and connection respectively played significant roles in predicting depression (p= 0/001), and totally explained 39% of the variance of depression. The components of family function including role, problem solving, and emotional expression respectively had significant roles in predicting depression (p= 0/001), and totally explained 25% of the variance of depression. Conclusions: Overall, the results indicated the importance of family function with emphasis on the components of positive youth development including competence, confidence, and connection in adolescent depression.