Refugees and migrants may encounter a variety of traumatic events, from the pre-migration to the post-migration phases of their journeys to safety, having fled conflict, war, human rights violations, and other life-threatening situations. These stressful and frightening events and their psychological sequelae can then adversely affect the refugees’ subsequent adjustment in their host countries and sometimes have longstanding mental health impacts. Post-traumatic stress disorder (PTSD) is only one of the outcomes following a trauma; however, it is important to discuss this concept in refugee and migrants because most PTSD guidelines were derived for mainstream populations. There have been concerns about the medicalization of suffering, and the exportation of a Western model of psychiatric diagnosis and treatment to non-Western populations. This chapter will review the concept of PTSD as a psychiatric diagnosis often associated with migrants and refugees, with acknowledgement of its history, prevalence, applicability to non-Western populations, and limitations in both diagnosis and management. The concept of ‘distress versus disorder’ will be discussed, as well as tracing back to the origins of PTSD and looking at issues of validity, culture, and phenomenology. Principles of management will be reviewed. The chapter will conclude with a section on resilience and post-traumatic growth.