Defining a clear, comprehensive, and non-overlapping set of assessment criteria is a crucial step in multi-criteria analysis processes. Although criteria are typically developed based on planning objectives, there currently exists no standard procedure for conducting this exercise when both transportation and wider sustainable development goals need to be considered jointly. Based on research applying the multi-actor multi-criteria analysis approach to the case of a high-speed rail project in the UK, this paper presents a framework and a replicable stakeholder involvement process for selecting, defining, and naming assessment criteria to be used in sustainable transport appraisal (STA). The framework consists of a set of systematic guidelines and considerations for producing a coherent list that addresses known cognitive biases and can be understood by a broad range of stakeholders. A further practicable outcome of the research is a comprehensive list, developed using this framework, of 28 transport assessment criteria encompassing direct project impacts, indirect societal impacts, and environmental impacts. This list can serve as a starting point for planners wishing to conduct MCA-based STA. One key take-away from this research is the emphasis on an inclusive, interactive, and iterative approach for defining sustainable transport assessment criteria.