Resumo BACKGROUND: The Dental Discomfort Questionnaire (DDQ) is an observational instrument intended to measure dental discomfort and/or pain in children under 5 years of age. This study aimed to validate a previously cross-culturally adapted version of DDQ in a Brazilian children sample. METHODS: Participants included 263 children (58.6% boys, mean age 43.5 months) that underwent a dental examination to assess dental caries, and their parent that filled out the cross-culturally adapted DDQ on their behalf. Exploratory factor analysis (principal component analysis form) and psychometric tests were done to assess instrument's dimensionality and reliability. RESULTS: Exploratory factor analysis revealed a multidimensional instrument with 3 domains: 'eating and sleeping problems' (Cronbach's alpha 0.81), 'earache problems' (alpha 0.75), and 'problems with brushing teeth' (alpha 0.78). The assessment had excellent stability (weighted-kappa varying from 0.68 to 0.97). Based on the factor analysis, the model with all 7 items included only in the first domain (named DDQ-B) was further explored. The items and total median score of the DDQ-B were related to parent-reported toothache and the number of decayed teeth, demonstrating good construct and discriminant validities. CONCLUSIONS: DDQ-B was proven a reliable pain assessment tool to screen this group of Brazilian children for caries-related toothache, with good psychometric properties.