Crime is a multifaceted phenomenon caused by a myriad of factors, including social, economic, and psychological factors. This study examined the predictors of criminal behaviour among teenagers in Kibera, Nairobi, Kenya. Kibera is the largest slums in Africa and is characterized by high poverty levels, high crime rates, unemployment rates, and limited access to basic amenities. The prevalence of crime in Kibera slum is marked by theft as the most reported crime and has drawn many teenagers into engaging in illegality as a way of earning a living. Notably, understanding these socio-economic and individual factors that contribute to teenage delinquency in Kibera is instructive in developing effective intervention and prevention strategies. This study was based on two objectives: examining the socio-economic factors and the individual-level factors that influence the adoption of criminal behaviour amongst teenagers in the Kibera slum. The strain theory was used to understand the relationship between the socio-economic and individual-level factors in the Kibera teenagers' context and the adoption of criminogenic behaviour. The case study design was adopted in which data was collected and analysed using qualitative methods. The data was collected from 19 participants, including teenagers, teachers, parents, guardians, and local administration officers. The sample was generated using purposive and snow-balling sampling with the questionnaire and focus group discussion used to collect the data. The study concluded that socio-economic factors influencing criminal behaviour amongst teenagers included access to education, economic instability, family dysfunction, peer pressure, community support, and school policies, while the individual-level factors included mental health issues, genetic variations, and prenatal and perinatal factors. The study recommended the establishment and implementation of programs to cater to economic impoverishment, educational access, role modelling, and mental health issues as necessary for tackling criminality amongst the teenagers in the Kibera slum