This study has aimed to investigate how a growing municipality defines social sustainability and what methodology is used to achieve this. The municipality of Skellefteå has been selected to be analyzed for this essay.  The method applied is a qualitative case study where four documents related to the municipality of Skellefteå and its planning unit have been analyzed. The documents that have been used for the study are the municipality's comprehensive plan, the public health policy program, their development strategy for 2030 and the digital citizen dialogue that formed the basis for the development of the strategy. To gain a deeper understanding of how the work on these documents is carried out and how they relate to social sustainability, two semi-structured interviews were conducted with two professionals who actively worked with the documents. What the study shows is that within recent years the work with social sustainability has been actualized and more visible within the planning unit and the municipality's work around the concept. Skellefteå's municipal growth has meant that the various documents within the municipality had to be updated for them to be adapted to the new conditions within the municipality. How it will be reflected later in the physical planning in the municipality remains to be seen as Skellefteå is still in an initial phase of the social transformation that has begun. Further research is proposed since each municipality is unique and that site-specific conditions need to be analyzed to apply social sustainability in the best possible way. Social sustainability is also a complex and broad concept, which makes it difficult to generalize conclusions based on this study.