Background: Although cognitive-behavioral therapy (CBT) is established as a first line treatment for anxiety disorders in children and adolescents, there is little evidence about the effectiveness of CBT protocols in cases identified in the community in low and middle income countries (LaMICs). Aims: To evaluate the effectiveness of group CBT protocol for youths with anxiety disorders identified in a community sample in LaMICs. Method: A total of 14 sessions of group CBT for youths and 2 concurrent sessions for parents based on Kendall's Coping Cat program were offered. Participants were selected from a cross-sectional community study; 45 subjects fulfilled inclusion criteria and 28 agreed to participate in the open clinical trial. Treatment effectiveness was evaluated with standard clinical, self- and parent-rated measures of anxiety, depression, externalizing symptoms and quality of life (QoL). Results: Twenty youths completed the protocol. All scales showed an improvement of anxiety and reduction in externalizing symptoms over time, with a moderate to large effect size (d = 0.59 to 2.06; p < .05), but not in depressive symptoms or QoL. Conclusions: Consistent with previous evidence, group CBT is effective in treating anxiety disorders in youths. Results encourage further randomized clinical trials using CBT protocols adapted and developed to be used in LaMICs.