This chapter will examine the psychological theories and constructs closely associated with juvenile delinquency, its causes, prevention, and treatment. First, the chapter explores two developmental theories, Urie Bronfenbrenner’s ecological theory and John Bowlby and Mary Ainsworth’s attachment theory. The former presents a contextual understanding while the latter takes an organismic approach to development. Besides this, we will review psychosocial constructs influencing juvenile delinquency and youth development, supported by empirical research such as aggression, emotional intelligence, and prosocial behaviour. The above developmental and psychosocial constructs will explore the causes of juvenile delinquency, prevention, and treatment