Objective: This study set to assess the effectiveness of cognitive-behavioral therapy in ameliorating GAD in adolescents. Method: The participants of the study comprised 62 girls with GAD that were selected by diagnostic interview and Penn State Worry Questionnaire and randomly assigned into experimental and control groups. In order to assess the effectiveness of CBT on decreasing anxiety, Cattell anxiety Questioners was used the before and after CBT. Results: t-test analysis showed a significant difference between the two groups. Conclusion: Cognitive-behavioral therapy could be suggested as a useful therapeutic method to treat anxiety in adolescents.