In spite of the growing awareness and significance of accounting for sustainability aspects in product development, design decision support is still immature in this end compared to other decision support areas, such as product performance and manufacturability. This paper proposes a novel decision support method that combines qualitative sustainability assessment techniques with a quantitative analysis, without losing transparency and still covering a full sustainability perspective. The aim is to contribute to an understanding for how to enable value assessment of sustainability issues already in early product development situations. The method, named Sustainability Assessment and Value Evaluation, combines two qualitative sustainability assessment techniques with a quantitative Net Present Value analysis based on alternative future scenarios. A case study, related to the development of a new high-temperature aero-engine component, illustrates both how the sustainability assessment identifies hotspots and clarifies potential sustainability consequences for a new product technology, and how Net Present Value is used to assess alternative solution strategies based on the hotspot, to facilitate early stage decision-making in design. The paper argues that the method serves two main purposes: i) to make sustainability consequences more concrete and understandable during design concept selection activities, rather than to have an exact measurement, and ii) to simplify and prioritize, systematically asking what is important in the sustainability analysis, rather than to reduce the sustainability problem. The method allows undertaking the sustainability assessment in a more structured way than what happens today in preliminary design, through scenario building based on socio-ecological assessments, including back-casting to cover the longer time perspective. In addition, the Sustainability Assessment and Value Evaluation-method provided the design team of a means for displaying sustainability consequences on an equal basis with other decision support tool results.