Earlier in this book, sustainability was introduced as a key principle of the bioeconomy. While bioeconomy systems are not sustainable per se, science-based assessment methods are required to address this principle in both novel and traditional bioeconomy systems. This chapter provides an overview of sustainability assessment methods that support the evaluation of products, services, systems and organisations within the bioeconomy. The chapter begins with a brief refresher on the concepts of sustainability and explains the relevance of sustainability assessment. It then characterises sustainability assessment methods, followed by an introduction to sustainability indicators as a means of quantifying different sustainability aspects. This brief overview is followed by dedicated sections on environmental, social and economic assessment methods with a focus on Life Cycle Assessments, Social Life Cycle Assessment and Life Cycle Costing. The concepts of end-point results, multi-criteria decision analysis and true cost accounting are also introduced, particularly in the context of improved communication. The final part of the chapter is dedicated to the use of sustainability assessment in the bioeconomy. Areas of application are described, and the challenges associated with the assessment of agricultural systems, novel technologies and regional specificities are highlighted.