Socialization is the process of adopting socially acceptable norms, rules and behaviors that are characteristic of a particular culture. As certain behaviors are adopted through socialization, the assertive behavior that we have identified as an object of this work is also developing. Assertiveness is a form of behavior that implies taking personal rights and expressing thoughts, feelings and attitudes in a direct, honest, moderate and convenient manner, with respect for other people (Kljajo-Nikolić, 2017). Apart from socialization and assertiveness, other forms of social behavior as well as the theories of social learning that are presented to us in more detail can be mentioned in the paper, which can influence the adoption and development of a certain behavior, specifically assertive behavior, as the theme of this work. As assertiveness is a form of behavior that, like norms and rules, is adopted through socialization, it raises the question to what extent and how socialization affects the development of assertive behavior. In addition, children around the second year show signs of innate assertiveness, and apart from primary socialization in the family, most are influenced by kindergartens and educators as means of socialization. Therefore, we have also outlined ways to encourage and develop the assertiveness in the preschool institution, which was also the subject of research in our work.