Research on child well-being under 10 years old is limited. A first step towards stimulating research targeting this population is the validation of psychometric scales across cultures. The current study examines the cross-cultural validity of the Children’s Worlds - Subjective Well-being Scale (CS-SWBS-8-year-old version), a six-item subjective well-being scale in an international sample of 8-year-olds (N = 20,822) across 19 countries. A confirmatory factor analysis of the CW-SWBS-8yo showed adequate fit after structural equation modelling. Multi-group analysis supported scalar invariance when one of the countries (Chile) was not included in the model. When testing convergent validity, results suggested that the CW-SWBS-8yo is predicted by life satisfaction, positive affect, and negative affect. Overall, the findings support the use of the CW-SWBS-8yo in 8 year-olds in both eastern and western countries.