Warning reports regarding rapid climate change have increased during the last year. Questions and interest regarding how public libraries work with sustainable issues have emerged.  The purpose of this thesis is to discuss how public libraries are working with sustainable development issues and whether the work can contribute to reaching UN Sustainable Development Goals.  The theoretical framework used in this thesis is the Four space model of the public library of Jochumsen, Hvenegaard Rasmussen and Skot-Hansen (2012). Data collection was made by using a qualitative method. Five librarians were chosen for interviews. The study want to answer following search questions: 

-    Is there work with sustainable development in relation to Agenda 2030 in public libraries and in such cases how?

-    How do public libraries promote their work with sustainable development to users and why?

The results suggest that public libraries are an important resource in the work of reaching the goals of Agenda 2030. Public libraries as an open sphere and promotor of free information access support all SDG Goals but in particular Goal 16 and target 16.10. The library is also a promoter of lifelong learning which supports SDG 4 mainly by offering services and programs to library users in either the physical or digital room of learning or meeting. The library promote their media, services and programs on social media in the room of inspiration and learning.