The Luxembourg COVID-Kids questionnaire was developed in 2020, during the COVID-19 pandemic by a multilingual team at the University of Luxembourg. It was based on existing validated questionnaires as well as qualitative research. Questions were selected to be relevant to cross-national comparisons. The questionnaire is currently available in Luxembourgish, German, Brazilian Portuguese, European Portuguese, French and English. It has been used in a large-scale international survey conducted in Luxembourg, Germany, Switzerland and Brazil (Engel de Abreu, Neumann, Wealer, Abreu, Coutinho Macedo & Kirsch, in prep; Kirsch, Engel de Abreu, Kirsch, Engel de Abreu, Neumann, Brazas & Wealer, in prep).