Background: The aim of this research was to investigate the effectiveness of play therapy with Filial therapy techniques on preschool children with oppositional defiant dirorder in city of Falavarjan. The research method is quasi-experimental with control group pretest posttest design

Method: . The statistical population of the study included all children with oppositional defiant disorder in Falavarjan city who referred to counseling centers in Falavarjan in 2017-2018 school year, and 30 of these children were selected using convenience sampling method and put into two control and experimental groups (15 in each group). The experimental group were presented with Filial therapy intervention program for 10, 1 hour sessions for 1 month, while the control group did not receive any intervention during the research process. In this study, the data collection tool was the attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) questionnaire by Swanson, Nolan and Pelham (1980) which was used on both control and experimental group in the pretest posttest stage. Data was analyzed by analysis of covariance using SPSS 24 software package.

Results: The results showed that Filial therapy intervention program has a significant effect on reducing children's oppositional defiant disorder (p <0.001). Based on the findings of the study, it is recommended to use the Filial therapy method.

Conclusion: play therapy in the form of filial therapy gives children the opportunity to freely explore their surroundings and communicate with family members in an environment free from threats and fear and develop their communication skills.