Studies of urban rural migration often find the most likely migrants are adolescents and young people. Yet few studies have explored patterns of adolescent migration and the role of migration in transitions to adulthood. This study uses data from a population-based survey of over 1000 adolescents aged 10–19 in slum areas of Addis Ababa. Twenty-three per cent of boys and 45 per cent of girls have migrated into the city, mostly from rural areas, mainly for educational or work opportunities. Nearly one quarter of female migrants moved to escape early marriage in their rural homes. Migrants in this study were more vulnerable than natives in terms of lacking of parental presence, schooling, and social connectedness. Such young people, most of whom are girls, are ‘falling through the cracks’ of policy and programs and in need of increased program attention.