The COVID-19 pandemic is harming health, social and material well-being of children worldwide, with the poorest children, including homeless children and children in detention, hit hardest. School closures, social distancing and confinement increase the risk of poor nutrition among children, their exposure to domestic violence, increase their anxiety and stress, and reduce access to vital family and care services. Widespread digitalisation mitigates the education loss caused by school-closures, but the poorest children are least likely to live in good home-learning environments with internet connection. Furthermore, increased unsupervised on-line internet use has magnified issues around sexual exploitation and cyber-bullying. Immediate government measures need to ensure that children have access to good food, receive protection against child abuse and neglect, have continued access to child physical and mental health services, and can navigate safely on the internet. Policies also need to support parental employment since it is key to fighting child poverty.