BACKGROUND: There is a need for a validated simple Dutch paediatric activity scale. The purpose was to translate and transculturally validate the Dutch Hospital for Special Surgery Paediatric Functional Activity Brief Scale (HSS Pedi-FABS) questionnaire in healthy children and adolescents. METHODS: The original HSS Pedi-FABS was translated forward and backward and was transculturally adapted after performing a pilot study among children and professionals. The final version of the Dutch HSS Pedi-FABS was validated in healthy children and adolescents aged 10 to 18 years old. Children who had any condition or injury limiting their normal physical activity were excluded. The interval between the first questionnaire T0 (HSS Pedi-FABS, Physical Activity Questionnaire for children or adolescents (PAQ-C/A) and Tegner activity scale) and the second questionnaire T1 (HSS Pedi-FABS) was 2 weeks. Construct validity, interpretability and reliability were evaluated. Content validity was evaluated through cognitive interviews among a smaller group of children and through a questionnaire among professionals. RESULTS: To evaluate content validity, 9 children and adolescents were interviewed, and 30 professionals were consulted. Content validity among professionals showed a relevance of less than 85% for most items on construct. However, content validity among children was good with a 92% score for item relevance. Readability was scored at a reading level of 11- to 12-year-olds. The validation group consisted of 110 healthy children and adolescents (mean age of 13.9 years ±2.6). Construct validity was considered good as 8 out of 10 hypotheses were confirmed. The Dutch HSS Pedi-FABS showed no floor or ceiling effect. Analysis of the internal consistency in the validation group resulted in a Cronbach's alpha of 0.82. Test-retest reliability was evaluated among 69 children and adolescents and revealed an Intraclass Correlation Coefficient (ICC) of 0.76. CONCLUSION: The Dutch HSS Pedi-FABS showed good psychometric properties in a ...