It has been observed that children find it difficult to search the library catalog, for example they have difficult to spell and have a lack of vocabulary. There is therefore a need to find out how the library catalog actually works in the public library. This thesis aims to contribute knowledge about how public librarians experience the utility of the library catalog for children in information seeking. Three questions were formulated to answer the thesis purpose, which are, factors affecting the usability, problems that can occur when children are using the library catalog and improvement opportunities for the library catalog.The theoretical framework used in this thesis is a model of Allwood that defines usability based on human-computer interaction (HCI). The method used is a qualitative semi-structured interview with five public librarians who works with children. The result showed that impact factors as physical availability, procurement of library system and the librarian’s active viewing of the library catalog can affect the usability. The problem mentioned is the language in the catalog, the number of steps in the search process and the link between the library catalog and the shelf. A conclusion, based on this thesis, is that more knowledge is needed about the usability of today’s library catalogs on how the technology can make it more useful for its users.