Impulsivity and aggression are the most challengeable problems both for adolescent and his/her parents. There are many interventions, medical or behavioral, for management and control of these situations. Mindfulness is cognitive-behavior intervention that can be effective, so the purpose of this study is to investigate the effectiveness of mindfulness in reduction of levels of impulsivity and aggression in adolescents. This is a pre-post experimental with control group study. The statistical community consists of all adolescents, who were at Tehran high schools between years 2011-12. 50 (25 control group, 25 experimental group) girl students (15-17 years old) were chosen randomly according to multiple stage cluster sampling method. In order to gathering data, Barat Impulsivity Scale & Aggression questionnaire were used. Mindfulness is based on stress reduction and cognitive-behavior therapy (8 weekly sessions). The validity of mindfulness was examined (20 adolescents), before the main study. The levels of aggression and impulsivity were assessed, after this intervention. Co-variance analysis and was used for data analysis. Results indicate that the effectiveness of Mindfulness in reduction of levels of aggression and impulsivity.