This paper introduces a new perspective on systems thinking in design related to sus- tainability. We argue that designers need to look at sustainability in an integrated man- ner where technical, economical and social aspects are embedded in an ecological ho- listic view. Sustainability is not just another requirement in the design process but needs to form the foundation for all design work. Systems-oriented Design is a new concept which is currently being researched and developed by the lead-author. It draws on existing concepts of systems approaches especially Soft Systems Method- ologies and Critical Systems Thinking and contributes by developing design proprietary methods, techniques and skills. By defining systems thinking as a design practice with its own particular set of methods and skills the approach becomes closely linked to a designerly way of thinking and making. The main aim of this approach is to involve deeper in all aspects of a design project. In this way the designer can be enabled to address a much greater complexity, to assimilate very large amounts of information and to produce new innovative interventions. We argue that these are requirements and skills needed for the designer to address sustainability in a holistic way.