Introduction: The purpose of the current study was to investigate the effect of training behavior modification methods to mothers of children with Attention Deficit Disorder (ADHD) on enhancing the behavioral performance and decreasing parenting stress.Method: The research method was quasi-experimental with pre-test and post-test design and cotrol group. To do so, 30 mothers of children with ADHD were selected using at-hand sampling and divided into control and experimental groups. Both groups filled out Parenting Stress Index and children behavioral performance questionnaire. In the next step, the experimental group was instructed behavior modification methods in 9 ninety-minute sessions while the mothers in control group went on their normal procedures. At the end of the instructional session, both groups filled out the mentioned questioners as the post-test. Covariance analysis was used for analyzing data.Results: The results of the analysis of covariance showed that instructing behavior modification methods improved behavioral performance in children and also decreased parenting stress among mothers in experimental group, in comparison with the control group.Conclusion: Findings generally showed that instructing behavior modification methods to mothers, reduces behavioral problems of children and prevents stress in child-parent relationship.