Juvenile delinquency and crimes creates enormous setbacks in the development process mostly in third world countries like Tanzania whose mechanisms to deal with the situation are weak. This paper examines the dynamics of juvenile delinquency and crimes and their mitigation measures in a study done in Arusha, Tanzania. The study results showed that juveniles involved in delinquent behaviours are as young as 12 years old, and most join the bandwagon after completion of primary school education. Poverty is the main factor for their involvement in juvenile crimes; and so are peer influence, drug abuse, and alcoholism. The paper recommends the design of comprehensive strategies to improve the roadmap to youth life, especially those who do not get an opportunity to join secondary education. Efforts that encourage strong family ties were found pertinent to deal with juvenile delinquencies and crimes. It is important to ensure that youth in Tanzania become an integral part of the development process as they form the largest proportion of the country’s population. Keywords: juvenile delinquency, crimes, peer influence, Tanzania