Qualitative methods for impact assessment (IA) represent a broad spectrum of approaches that are important for realising effective IA practice. The purpose of this paper is to identify and promote qualitative methods that are available for use in contemporary and future (next-generation) IA processes. From an extensive literature review, an international survey (145 responses), expert interviews (48 interviewees), and a workshop attended by 27 IA practitioners, 17 qualitative method categories were identified. These were further subdivided into three classes: conventional qualitative methods, highly participatory methods, and mixed methods. Each method is described, and an indication given of how each can be used in IA practice, including the specific stage of the IA process to which they might be applied. Whilst this paper seeks to stimulate practitioners to apply qualitative methods to enrich IA practices, the research also identifies a lack of expertise with social science methods as a significant barrier to the effective use of qualitative methods in IA practice.