Introduction: The purpose of the present research was to investigate the effect of Positive parenting program (Triple-P) on decreasing the symptoms of ODD in 6-7 year-old children. Method: An experimental and a pretest-posttest control group design method have been applied in this regard. Participants of the study were all parents of 330 children who were at pre-school grade and also first grade in the school. To find and select the main subjects, two steps were taken, At the first step, the selected parents were those whose children gain the scores higher than cut-off score in Children Behavior Checklist (CBCL), and at the second step, for final selection, these chosen parents were attended in the Structured Diagnostic Interview-based on DSM-IV-TR criteria. Main subjects were finally, those parents whose children's disorder symptoms were confirmed through the diagnostic interview selected and divided randomly to two experimental (25 people) and control group (21 people). The experimental group received Triple-P and control group received no intervention. Results: The analysis showed that the children of mothers who were in experimental group had a significant decrease in the symptoms of ODD , while the children of mothers in control group showed no significant difference. Conclusion: Although there were cultural and social differences between the studies groups of this research and those groups in other communities and cultures, there was a significant decrease in the symptoms of ODD in the children of mothers in experimental group.