Sustainability has been extensively studied in different disciplines especially since the publication of the Brundtland commission’s report in 1987. However, in public management as well is knowledge management literature sustainability has gained limited scholarly attention. Especially, there is a lack of understanding of sustainability as an issue that needs managing. Therefore, article approaches sustainability in organizational context and is interested in how sustainability is managed in local government and what knowledge is used to support management. While sustainability can be regarded as a pressing societal challenge, relatively little is known on how sustainability policies and strategies are implemented and managed in public organizations. In order to understand how public managers perceive sustainability as a management issue and define sustainability information, an interview study was carried out. The article analyses the data of 25 semi-structured interviews from branch and financial directors in Finnish municipalities to provide an in-depth knowledge-based view to the practice of managing sustainability in local government. The article contributes by developing new understanding about the different roles knowledge management can have in supporting public organizations and public officials to grasp the complex phenomenon of sustainability.