Since its inception, impact assessment (IA) has been perceived by many to be a largely technical, quantitative exercise. However, as jurisdictions shift towards a more sustainability-oriented IA that accounts for a wider range of social, cultural, economic, health and well-being, and equity implications of proposed projects and strategic initiatives, values and subjectivity come more to the fore. Making predictions now needs innovative, and rigorous applications of qualitative methods that enable meaningful inclusion of diverse knowledges, values, and information sources, whilst at the same time giving confidence to decision makers and other stakeholders about the evidence base. Adopting such qualitative methods in practice is hindered by a lack of clarity of the role of qualitative methods in the delivery of sustainability-oriented IA. Guided by findings from a thematic analysis of primary data gathered through an international survey supplemented by semi-structured interviews and a workshop, the novel contribution of this paper is to clarify how and why qualitative methods can best contribute to the effective delivery of next generation IA.