Introduction: Adolescence is a critical period featured with considerable physical, social, and psychological changes. Low self-esteem along with problems in social and personal relationships may lead to mental disorders. The present study is aimed as surveying the effectiveness of group cognitive therapy on self-esteem of second-level high school girl students. Methods: The study was conducted as an experimental work with control group. Out of two girls high school in Gotvand City one school was selected to form the control group and another school was selected to form intervention group randomly (2014-2015). Afterward, based on inclusion criteria, 32 participants (16 in control and 16 in experiment groups) were selected. “Cooper Smith’s self-esteem” questionnaire was filled out by the participants of the two groups. The intervention group took part in 8 sessions (90mins each 2 sessions per week) of cognitive group therapy. Posttest and follow up test were taken immediately and one month of the intervention from the both groups. The collected data was analyzed through variance analysis with frequent measurements in SPSS (20). Results: The results showed that there was no significant difference between the two groups at pretest regarding self-esteem score (p = 0.26) while, after the intervention and at follow stage, there was significant difference in this regard between the two groups (p=0.05). Conclusion: Cognitive group therapy resulted in increase of self-esteem of the juvenile. Future studies may focus on longer follow up periods to ensure of persistency of the results.