Objective: The present study aims at investigating the effects of behavioral therapy techniques through operant conditioning and observational learning on children's aggression aged 4-6 years. Methods:To this end, a pretest-posttest quasi-experimental study with two experimental groups and a control group was designed. We used non-probability purposive sampling method to select 45 mothers of aggressive children out of all mothers in Deylam City, Iran. They were randomly assigned into three groups (each group included 15 participants). Primary data were collected using the questionnaire developed by Vahedi, Fathi-Azar, Hosseini-Nasab, and Moghadam (2008). To analyze the data, multivariate analysis of covariance, 1-way analysis of covariance, and Bonferroni tests were used. Results:The results indicated that teaching operant conditioning and observational learning techniques to the mothers reduced their children's overall aggression along with its components, including verbal-offensive, physical-offensive, and relational aggression as well as impulsive anger. Conclusion:These techniques are recommended to be used in clinical interventions to teach the families how to control their children's aggression.