Juvenile delinquency is represented by those socially dangerous behaviors that are criminalized by law. The term criminality is usually used when it comes to adult perpetrators of criminal and other punishable acts, while delinquency is used when it comes to juvenile perpetrators. Also, juvenile delinquency is conceptually defined and its causes are studied along with statistical data on juvenile delinquency in the Republic of Croatia. Then the characteristics of pre-delinquent and delinquent behavior are described and the model of risk and protective factors is studied. Special emphasis is placed on two important determinants of juvenile delinquency: the limits of juvenile delinquency and the behavior of juveniles that are considered delinquent. After a brief overview of the forms of pre-delinquent and delinquent behavior, the paper discusses the theories of delinquent behavior. In this sense, biological and psychological theories are mentioned, and special importance is given to sociological theories: Anomie theory (Merton), Subcultural theory (Cohen), Differential Association (Sutherland) and Identification theory. The causes of juvenile delinquency are divided into external and internal. From the external causes the influence of family, school, peers, climate and geographical location, economic conditions, urbanism and migration are analyzed. Intelligence, genes, emotions and motivation are taken as important internal causes. The crucial importance of family, school and peers in the upbringing of minors and the development of delinquent behavior is concluded. The socioeconomic status of the family, upbringing style, family structure and possible antisocial and pathological phenomena are studied as fundamental family factors. In addition to positive family upbringing, school is seen as an ideal place to rehabilitate the problematic behavior of young people. When analyzing the internal causes, it is concluded that motivation and the so-called the struggle of motives should be given attention when studying the emergence of delinquent behavior.