Mass displacement is a major global challenge and the number of people who have been forced to flee their homes has doubled in the last decade to more than 100 million. Sudden population changes (both influx and exodus) impact the efficient functioning of the built environment and this affects social relations between host and displaced communities. In ameliorating negative impacts and fostering social cohesion, built environment professionals have an important role to play and they need to better understand mass displacement. This research investigated the role of built environment professionals in responding to mass displacement, identified requisite competencies and derived a competency framework. The competency framework was developed in a two-phase process. In the first phase, the types of built environment professionals and the scope of their competencies relevant to mass displacement were identified enabling an initial competency framework to be conceptualised and data collection tools to be developed. The second phase was aimed at developing, refining and then validating the competency framework. It employed a Delphi technique in which an international panel of 19 experts was established and responded to 3 rounds of progressive questioning using online questionnaires. While country contexts were found to differ considerably in terms of their direct involvement in mass displacement-related activities, built environment professionals do have an important role to play in mitigating the effects of mass displacement and promoting social cohesion between displaced and host communities. That role relates primarily to enabling displaced people to access services through the provision of the necessary infrastructure to deliver services (e.g., housing, transport, schools, etc.) and, also, through the appreciation of the interrelationships that exist between these accesses (e.g., language, transport, health and employment). Of the relevant competencies identified, a significant proportion of these were relevant to all professionals (not just built environment professionals) and related to their need to understand the mass displacement context. Further competencies identified were particularly relevant to built environment professionals and some were found to be occupation-specific in their relevance. A hierarchical competency framework was derived comprising 3-tiers of competencies: 1. Foundational competencies (of relevance to all professionals with an interest in mass displacement); 2. Industry-wide competencies (applicable to all built environment professionals); 3. Occupational competencies (applicable to a subset of built environment professionals). The resulting competency framework has subsequently provided the basis for developing a series of training courses and for the formulation of competency recommendations to built environment professional bodies.