Introduction: Separation anxiety is the most common anxiety disorder in children. The neglect of treatment of this disorder at early ages could be a risk factor for other childhood and adult psychological disorders. The purpose of this study was to examine the efficacy of Coaching Approach Behavior and Leading by Modeling (CALM Program) on reduction of the symptoms of separation anxiety disorder among preschool children. Materials and Methods: The research plan was designed as pretest-posttest with control group. The sample included 30 children with separation anxiety disorder. Children were selected by multi-stage cluster sampling method and assigned randomly in the experimental and control groups (each group 15 individuals). CALM-based treatment program for each participant of experimental group was conducted across 12 sessions, in the form of mother-child interaction. Spence Children's Anxiety Scale (parent form) was used to measure the severity of separation anxiety disorder. Results: CALM-based treatment interventions created a significant reduction in the symptoms of separation anxiety in the experimental group compared to the control group on the post-test and follow-up stages. Conclusion: CALM-based treatment interventions can be used as applicable and effective treatment for reduction of the symptoms of separation anxiety in preschooler children.