The objective of the study was to evaluate the effectiveness of cognitive behavior therapy (CBT) for the children suffering from anxiety disorders. For conducting the study 109 children and adolescents aging 717 with primary diagnosis of anxiety disorders from five government and nongovernment institutions were randomly allocated to CBT based treatment group (TG) or a waitlist group (WLG). CBT based Cool Kids Anxiety Program was used for intervention purpose. Assessment data during preintervention, postintervention (2 and ½ months from preintervention) and followup( 1 month from postintervention) were collected from both of the groups. It was found that the symptoms and comorbid other internalizing (depression, cognitive bias) and externalizing problems (negative behavior) decreased significantly in the CBT group or TG after the intervention according to both child and parent report when there was no significant change in symptoms in the waitlist group. The study contributes to the evidence base for using CBT as an effective intervention process in treating the anxiety disorders of the young population of our country.