Data are foundational to upholding the rights of all children – particularly when it comes to marginalized groups like children on the move. But vast differences in the way governments collect, analyse and use data related to migration and displacement result in inherent limitations and inaccuracies behind the numbers they produce. This means that global estimates of migrant and displaced children compiled by various United Nations bodies – which are based on reports submitted by individual governments – are far from complete. This publication takes a close look at the existing and emerging sources behind data and statistics on migrant and displaced children in order to close these data gaps and improve methodologies. It unpacks the strengths and limitations of key data sources on children on the move and showcases examples of promising national-level initiatives taking place to improve data for this group. An extensive list of databases and resource hubs that publish data and statistics on migrant and displaced children is also featured in this reference document.