The Distress Tolerance Scale (DTS) was adapted for American and Chinese youth, but never for European youth. Moreover, the factor structures found in these previous studies were not consistent. The DTS was adapted for Portuguese children and then validated among 153 children aged 6-13 years with emotional disorders. A confirmatory factor analysis (CFA) was conducted; the DTS reliability and validity were analyzed, and sex and age differences were explored. A sub-sample of children who received a transdiagnostic CBT (Unified Protocol for Children) was used to analyze the DTS's sensitivity to therapeutic change. The five tested models (based on previous studies) exhibited adequate fit in the CFA. However, the model previously reported for use in American children with emotional disorders was selected as the most appropriate. The DTS demonstrated adequate psychometric properties, and its validity was established through significant negative associations with measures of anxiety, depression and negative affect, as well as positive associations with positive affect. Age and sex differences were discussed. The DTS scores significantly increased from pre- to post-treatment, demonstrating sensitivity to therapeutic change. The DTS is a suitable and useful measure for assessing children's distress tolerance and to assess the efficacy of CBT.