We present the process of evaluation and treatment of two polyglot girls of five and seven years of age. Both met the criteria for the diagnosis of selective mutism (APA, 2013). The intervention was carried out with the participation of the family and the school. A cognitive behavioral treatment was designed and later applied in a differentiated manner to adults and girls. Adult training included transmission of information, instructions, cognitive restructuring and modeling; treatment for the girls included stimulation fading, economy of cards, response cost, and exposure to be seen and heard talking to other classmates in their respective classrooms. The results show a normalization of audible speech in response to external requests in class and on the playground, the appearance of spontaneous speech, the increase in play and the elimination of social isolation. These results were maintained in the follow-up measures at 3, 6 and 12 months. The treatment has shown its efficacy in the complete remission of the disorder in both cases.