In 2015 the UN initiated the project Agenda 2030, which aims for all countries to work together for a sustainable world based on social, environmental and economic aspects. There is a known potential of the libraries role and opportunities to influence and work for sustainable development. Despite that, there is lack of policies and control documents for Swedish public libraries and work for sustainable development. There is also a lack of studies which shows how Swedish public librarians describe their work for sustainable development in public libraries and their driving force. The aim of this study is to contribute with knowledge about that work. Seven public librarians were interviewed. The interviews were analyzed with the help of practice theory and the three aspects of sustainable development. The result of the study showed that all partaking librarians have a big personal interest of sustainability, which they brought in practice of their daily work. Their actions, most regarding environmental and social sustainability, is grounded on value of solidarity and their professional knowledge, but also a personal knowledge of environmental issues. The study also showed that the few identified control documents were general policies for all activities in the municipality and not unique for the public libraries. The partaking librarians wanted more specific guidelines for their work with sustainable development, which they want to develop and work more with. With the help of librarians, guidelines can be drawn up and make the work clear, visible and possible to evaluate, as part of a social responsibility.