As the number of newly arrived minors (NAMs) has rapidly grown in Europe over the past decades, researchers have started to address the health consequences of migration for children. While extensive attention has been devoted to the mental and physical health of NAMs, little empirical work has focused on their social well-being. However, theoretical insights suggest that NAMs are at a double jeopardy of loneliness, because of their age and migration status. Moreover, loneliness among NAMs is of major concern, as it could exacerbate existing ethnic inequalities in mental health, physical health and school outcomes. To our knowledge, this project will be the first to explore experiences of loneliness among NAMs. The aim of the project is threefold. First, we will estimate prevalence rates of loneliness in NAMs and identify migration-related characteristics associated with loneliness. Second, we will investigate whether school social capital protects against experiences of loneliness. Third, we will explore the mechanisms behind the association between school social capital and loneliness. To achieve these objectives, we will carry out a mixed-method study in secondary schools providing reception programs. Qualitative data will be collected to provide further depth to quantitative findings. The research evidence can guide policy interventions aimed at improving NAMs’ social well-being and related factors, such as mental health, integration and academic achievement.