This thesis presents a study of street children’s involvement as workers in Bangladeshi organised crime groups, based on a three-year ethnographic study in Dhaka. The study focuses on the views and experiences of 22 children from the streets and slums. Drawing on participant observation and group interviews with the children, the study explores how these children perceived organised crime and why young people become involved in these groups. It argues that children’s perspectives are essential, even when the subject under discussion is the adult world of organised crime. The study also utilises data drawn from interviews with 80 criminal justice practitioners, NGO workers and community members and three years of participant observation of the Bangladesh criminal justice system and wider society. This thesis offers five main contributions to knowledge. Firstly, the study documents the ways that Bangladeshi organised crime groups – the mastaans – operate. It explores how these groups are structured, the crimes they commit and their subculture. Secondly, the study demonstrates that mastaans are ‘mafia-type’ organisations that operate in a market for social protection and are involved in a range of criminal activities. Thirdly, the study explains how street children work as labourers within these crime groups. They are hired to carry weapons, sell drugs, collect extortion money, participate in ‘land grabbing’, conduct contract killings and commit political violence. It argues that mastaan groups offer street children a way to earn money and access patronage, protection and inclusion. The study concludes that these children are neither victims nor offenders; they are instead ‘active social agents’, doing what they can to protect themselves and survive on the streets. Finally, the study contributes to literature on research methodologies, because it was the first to employ an empirical case study design to explore the relationship between street children and organised crime in Bangladesh.