Abstract. The present study aims to explore the effectiveness of Metacognitive Therapy on reducing the symptoms of student with Oppositional Defiant Disorder (ODD). Having a quasi-experimental nature with pre-test and post-test, the methodology consists of a two-month follow-up period and a control group. The statistical population includes all male secondary school students with Oppositional Defiant Disorder studying at 7th and 8th grades in Tehran during the educational year 2013- 2014. Using multi-stage cluster sampling method, a total of 30 subjects were selected and randomly assigned in the two experimental and control groups. The Child Behavior Check List was used to evaluate the rate of Oppositional Defiant Disorder in students. To analyze the statistical data, a covariance method was applied as a result of which a meaningful reduction (p>0.001) was observed in the post-test and follow-up intensity of ODD symptoms for the experimental group in comparison to the control one. Moreover, Metacognitive therapy proved to be an effective intervention in reducing the symptoms of ODD.