Organizational culture is dominant, complex but also unavoidable concept in analyzing organizational effectiveness and organizational development. Organizational culture is the one that affects the behavior of all members of the organization, and they, by accepting a system of standards that it sets, create an organizational climate. This paper is defining the concept of organizational culture, its origin and the elements and dimensions, functions, models, categories and types, as well as, some of the instruments used in the research of its types. All of the listed classifications, levels and structures, presented in this work will try to provide a better explanation of how organizational culture works. Given that in the field of culture and education as well as in librarianship there is rarely conducted research on organizational culture, partly because it is mostly associated with the management and commercial companies which are turned to the market and because of its complexity and multidimensionality, which makes it difficult to define, a study conducted in the City and University Library Osijek is of great importance, because it is an attempt to define its culture. For this reason, the work highlighted precisely this study so that its analysis could confirm the importance of familiarizing with the concept of organizational culture one belongs to as a basis for adjustment and development.Organizational Culture, researching Organizational Culture, City and University Library Osijek, OCAI