In contrast to the expected tasks and responsibilities, the informal role is the model of interpersonal behaviour that a team expects from the team member, based on the impressions they create as they work together. In other words, informal roles are spontaneous roles as a result of the relations of the members of the organization. The aim of this study is to investigate the informal role patterns affecting the efficiency and effectiveness of the organizations in the light of the studies conducted in the literature. In this context, it is aimed to investigate the informal roles of the individuals who are present in the socio-cultural structure in addition to their formal role behaviours. This research is discussed within the framework of four questions. These questions are "What does formal and informality concepts mean in management?", "What are the approaches related to the concept of informality?", "What is the concept of informal role?" and "What kind of informal role patterns occur between the groups and the employees in organizational life and how does it affect the organization?", respectively. As a result of the study, it has been revealed that informal roles have some advantages and disadvantages for organizations. For this reason, in particular with the managers of the organization, all employees need to be aware of the informal roles that support or undermine formal roles. [ABSTRACT FROM AUTHOR]