The present study was conducted to investigate the effectiveness of unified trans-diagnostic treatment on alexitimia and internalized behavioral problems of adolescent of divorce. The current study was a semi-experimental application with a pre-test-post-test design with a control group and a two-month follow-up period. The statistical population of the present study was formed by the adolescent of divorce in the first period of secondary education in the 14th district of Tehran in the year 2022-2023. 36 adolescent of divorce were selected through purposive sampling method and randomly accommodated into experimental (18 people) and control groups (17 people). The experimental group received ten ninty-minute sessions of unified trans-diagnostic treatment during ten weeks. The applied questionnaires included Alexitimia Questionnaire (AQ) and Children and Adolescents Behavioral Inventory (CABI). The results showed that unified trans-diagnostic treatment has significant effect on the alexitimia and internalized behavioral problems of adolescent of divorce. According to the findings of the present study it can be concluded that unified trans-diagnostic treatment can be used as an efficient method to decrease alexitimia and internalized behavioral problems of adolescent of divorce through Identifying emotions, teaching emotional awareness, cognitive re-evaluation, identifying patterns of avoiding emotions and examining behaviors caused by emotions.