Introduction. This thesis intends to examine and problematize a phenomenon that, until now, has not been the subject of research: the use of temporary employment agencies in Swedish public libraries. The aim of the study is to investigate how the motives for using temporary employed library staff can be understood in relation to two potentially conflicting institutional logics: the market-liberal oriented New Public Management (NPM) logic and the professional library logic. Furthermore, the study aims to examine how these two logics are used as a means of obtaining legitimacy. Theory & Method. The theoretical underpinnings of the study are new institutional theory, and the research method is document analysis. The study’s empirical material consists of public documents, which have been processed through a qualitative thematic content analysis. By focusing on one specific organization - The City of Stockholm public libraries (Stockholms stadsbibliotek) - the investigation is carried out as a case-study. Results & Analysis. Six main themes have been identified: resource efficiency, flexibility, open libraries, competence, stability and administration. All themes contain expressions of both institutional logics. Legitimacy is obtained partly through the NPM logic and in relation to cost efficiency, partly in relation to the professional and democratic principles of the library logic. Thus, both logics are applied to justify the use of temporary employment agencies. Conclusion. The studied documents contain a relatively stable dynamic between the NPM logic and the library logic. Contrary to what some new institutional theorists have argued, the study’s results indicate that multiple logics may be able to coexist within an organizational field. The explanation for the coexistence of these logics might be that they share certain aspirations and perceptions, for example the perception of the library users and administrative work.   This is a two years master’s thesis in Library and Information Science.