Depression is one of the most common psychological disorders. In recent years, cognitive-behavioral group therapy has received more attention for treating depression. The main purpose of present study is to examine the effect of Cognitive-Behavioral Therapy (CBT) on reducing depression among girl pupils of Junior high schools of Tehran city. The method of research is quasi-experimental. Multiple Cluster Sampling technique was employed to select 16 pupils and then they were randomly divided to each of control and case groups. After participation of experimental group at CBT meetings, all of the participants took pre-test and post- test. Data were analyzed using dependent t- student test. The findings revealed that there is significant difference between two groups at pre- post test results regarding Back Depression Inventory. The findings of present study provide empirical supports for the effects of CBT on girl pupils' depression reduction at junior high schools.