Background and Purpose: Considering the results of different studies indicating emotion regulation difficulties in children with Attention Deficit/ Hyperactivity Disorder (ADHD), efforts are made here to determine the effect of cognitive emotion regulation training on the anger of boys with ADHD. 
Method: This study was a quasi-experimental study with pretest-posttest control group design. The sample consisted of forty 12-year-old primary school boys with ADHD in Tehran in the academic year 2016-2017, selected by multi-stage cluster sampling and then randomly placed into the control and experimental groups. After running the pretest on both groups, the experimental group underwent twelve 45-min sessions of cognitive emotion regulation training while the control group received no intervention. Questionnaire of Children's Behavioral Problems- Parent Form (Conners, 1970) and State-Trait Anger Expression Inventory (Spielberger, 1999) were used to gather the data. ANCOVA was used to analyze the data.    
Results: The results of data analysis showed that cognitive emotion regulation training significantly decreased the anger in boys with ADHD (F=27.83, p> 0.05).
Conclusion: Students with ADHD are not so much capable to control their negative emotions. Cognitive emotion regulation training can reinforce the positive emotions in these children and led to the reduction of anger in them.