Our unsustainable way of living has created a precondition for the emergence of more and new illnesses, jeopardizing the overall health of society. The Swedish healthcare system faces complex challenges that threaten its ability to live up to its obligations as stated in the law. It is proven that leaders in public organisations can have a substantial function in leading towards sustainability. Leadership competencies have a big role to play in that journey.This thesis explores the complex challenges administration leaders in the healthcare sector of two Swedish public organisations – Region Blekinge and Västra Götalandsregionen face when it comes to sustainability. The Framework for Strategic Sustainable Development is used to analyse the complexity and the sustainability within the study’s context. The Framework of Sustainability Research and Problem-solving Competence is utilized to understand the application, the relevance of the key competencies in sustainability in leadership, as well as the barriers in applying them, to deal with challenges. The conclusions are based on documentary analysis and semi-structured interviews. The results show the need for all key competencies, with biggest emphasis being put on systems thinking, interpersonal, intrapersonal and implementation. The findings reveal potential enablers and barriers for the organisations in moving society towards sustainability.