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• A model for the population dynamics of age-structured criminal gangs with correctional intervention measures is proposed. • The existence of backward bifurcation is determined by the adolescent population. • We fitted the gang model against the crime data and provide forecast for the cumulative number of reported cases. • Global sensitivity analysis is carried out to determine the parameters that strongly drive the dynamics of the model. • The existence of periodic trajectories (Hopf bifurcation) for the criminal gang model is studied. The prevalence of criminal gang activities in the society has continued to be a huge burden to mankind. Despite several attempts by the government and non-governmental organizations in curtailing the activities of criminal gangs, new criminal gangs are beginning to emerge with associated criminal cases on the high side, thereby causing social unrest. This paper examines the impact of correctional intervention measures on the population dynamics of the criminal gangs in Nigeria, following an age-structured paradigm. The existence of backward bifurcation is presented sequel to the coexistence of gang free equilibrium and gang endemic equilibrium when the reproduction number is less than unity. Also, the model exhibits periodic trajectories (Hopf bifurcation) as a result of coexistence among the criminal gang classes. Using the Nigeria crime data (from 1993 to 2013) as obtained from Elsevier Data in Brief, we analyze the criminal gang model quantitatively and provide the sociological implications of the results. The numerical results obtained from this work show that if at least 60 % of adolescents between 8–17 years who commit crimes are apprehended with prompt prosecution and correction, we can potentially eradicate adolescent delinquencies from the population and thus control the entire criminal gangs' population. [ABSTRACT FROM AUTHOR]