Abstract Objectives: The main purpose of the current study was to perform the cross cultural adaptation and validation of the Activities Scale for Kids (ASK) both in its capability and performance versions to the European Portuguese language so it can be used in Portugal by healthcare professionals in children from 5 to 15 years of age with functional disabilities related to specific health conditions. Methods: The cross-cultural adaptation of ASK followed the classic sequential methodology for linguistic equivalence. To test its validity, internal consistency, and reproducibility, the Portuguese version of ASK was administered together with the KINDL Questionnaire (KINDL) to 88 children (10 ± 3 years of age) with functional limitations. The test–retest study was conducted two weeks apart. Results: After obtaining the semantic and content validity, the Portuguese version of ASK demonstrated good levels of reproducibility (performance: intraclass correlation coefficient [ICC] = 0.99; capability: ICC = 0.98) and internal consistency (performance: α = 0.98; capability: α = 0.97). The correlations between ASK and KINDL were positive and moderate. Conclusions: The Portuguese version of ASK showed acceptable levels of validity, internal consistency, and reproducibility; the authors recommend its use in clinical settings.